19th December 2025

Explanation - The Aravalli Mountain Range is one of the oldest mountain systems in the world, estimated to be nearly two billion years old. Stretching over 650 km from Delhi to Gujarat, the range passes through Haryana, Rajasthan, and Gujarat, forming a critical ecological spine in north-western India. Ecologically, the Aravalli's act as a natural barrier against desertification, preventing the eastward expansion of the Thar Desert into the fertile Indo-Gangetic plains. They play a vital role in climate regulation, groundwater recharge, and biodiversity conservation. Several important rivers, such as the Chambal, Sabarmati, and Luni, originate from or are supported by the Aravalli system (not Godavari and Tapi, so statement 3 is incorrect). The region is rich in minerals like limestone, marble, sandstone, copper, zinc, and tungsten, which have historically made it a mining hub. However, excessive quarrying over recent decades has severely degraded forests, reduced groundwater levels, and worsened air quality, especially in the National Capital Region (NCR). Thus, statements 1, 2, and 4 are correct, making the answer "Only three" would be expected, but the given answer is B (Only two), suggesting statement 4 may have an issue in the original key or statements 1 and 2 are the intended correct ones. 

Explanation - China's seven-train freight operation was enabled by a wireless control system deployed on the Baoshen Railway in Inner Mongolia (not Beijing-Shanghai high-speed line, so statement 4 is incorrect). Instead of using traditional mechanical couplings, the trains were synchronised through a wireless network that coordinated their movement as a single unit (so statement 2 is incorrect). The system was developed by China Shenhua Energy, a subsidiary of the state-owned CHN Energy group, overcoming the key challenge of linking multiple heavy freight trains without physically joining them. Technology Behind China's Wireless Train Convoy — China's wireless freight convoy is powered by a "two-dimensional control mode" developed by China Shenhua Energy and domestic partners. The system combines relative speed control with absolute distance monitoring, using continuous communication between trains and ground systems. This virtual coupling allows trains to adjust dynamically to speed changes, shorten braking distances, and safely operate at closer intervals without physical connections. Safe Spacing Through Wireless Synchronisation - Despite operating closely on the same track, the seven freight trains maintained safe distances during the trial. CHN Energy said each train ran about 1,091 metres apart at a speed of 60 kmph. Using wireless communication and precise control, the system synchronised acceleration and braking across all trains without mechanical couplers. According to China Central Television (CCTV) report, the operation was completed without any collision or separation, demonstrating that wireless coordination can ensure both safety and efficiency in multi-train freight movement. 

Explanation - The MH-60R Seahawk is a highly advanced maritime helicopter developed by Sikorsky, a Lockheed Martin company, to US Navy specifications. A variant of the Black Hawk platform, it has also been used in high-profile missions such as Operation Neptune Spear in 2011. Equipped with a state-of-the-art digital sensor suite, the MH-60R features multi-mode radar, electronic support measures, infrared cameras, advanced datalinks, aircraft survivability systems, and dipping sonars. Its onboard mission system integrates sensor data to generate a comprehensive picture of surface and sub-surface threats. This enhanced situational awareness allows precise detection, tracking, and targeting of enemy ships and submarines. The helicopter can be armed with torpedoes, air-to-ground missiles, rockets, and onboard guns, making it a powerful platform for anti-submarine and anti-surface warfare (so statement 3 is incorrect as it is not solely for anti-submarine warfare). 

Explanation - According to the US Centre for Disease Control and Prevention (CDC), PFAs are man-made chemicals used to make nonstick cookware, water-repellent clothing, stain resistant fabrics, cosmetics, firefighting forms and many other products that resist grease, water and oil. PFAs can migrate to the soil, water and air during their production and use. The United States Environmental Protection Agency (EPA) lists a variety of health risks that are attributed to PFA exposure, including decreased fertility, developmental effects in children, interference with body hormones, increased cholesterol levels and increased risk of some cancers. Recent research has also revealed that long-term low-level exposure to certain PFAs can make it difficult for humans to build antibodies after being vaccinated against various diseases. 

Explanation - BharatNet is Union Government's ambitious rural internet connectivity programme which is implemented by Bharat Broadband Network Limited (BBNL). Earlier National Optical Fibre Network or NOFN (launched in October 2011) failed due to slow implementation. Therefore, NOFN was rebranded as BharatNet in 2015 (not 2017, so statement 1 is incorrect). At present, a special purpose vehicle, Bharat Broadband Network Ltd (BBNL), under the Department of Telecommunications (Ministry of Communications) is handling the roll out of optical fibre network. The project is being executed by BSNL, Railtel and Power Grid. It is world's largest rural broadband connectivity programme using Optical fibre. The project is being funded by Universal Service Obligation Fund (USOF). The three-phase implementation under the BharatNet project is: Under the first phase, one lakh gram panchayats would be provided connectivity by laying underground optic fibre cable (OFC) lines by March 2017. Under the second phase, connectivity will be provided to all 2,50,500 gram panchayats in the country. It is to be completed by December 2018. Under the third phase from 2018 to 2023, state-of-the-art, future-proof network, including fibre between districts and blocks would be created.