Answer: C

Explanation:

They are much cheaper than military aircraft; and being flown under remote control, the flight crew faces no danger. Unmanned aerial vehicles (UAVS), also known as drones, are aircraft that are controlled from the ground; or they may be autonomously following a pre-programmed mission. Drones are mainly of two categories: those used for reconnaissance and surveillance purposes and those that are armed with missiles and bombs. Hence, statement 1 is correct.

Drones are increasingly being put to use because they can stay aloft for many hours, unlike manned aircraft; they are much cheaper than military aircraft; and being flown under remote control, the flight crew faces no danger. Hence, statement 2 is correct.

Answer: B

Explanation:

In March 2015, the fertiliser ministry ordered all the indigenous producers of urea in India to produce 75 per cent of their total production of subsidised urea as Neem Coated Urea (NCU), which is likely to save Rs 6,500 crore subsidy outgo. It would also help in soil conservation and check the diversion of urea for industrial uses. Farmers use urea in place of other partially decontrolled NPK (nitrogen, phosphorous, potash) fertilisers due to its highly subsidised price and this has resulted in imbalancing the ideal ratio of 4:2:1 of NPK. Hence, statement I is correct.

In order to keep the nitrogen losses at minimum level, agricultural scientists have come out with various agronomical recommendations, such as split application, band placement, and deep placement using the see drill. Various kinds of nitrification inhibitors such as Nitrapyrin (N-Serve) and Terrazole (Dwett) were developed in USA. But these nitrification agents are very expensive. In India, use of neem oil in various forms such as neem oil cake, neem oil and other neem products have been found useful in reducing the release of nitrogen from urea and increasing its use efficiency. Neem oil contains meliacins that have been identified in retarding the process of nitrification of urea. Hence, statement II is correct.

Answer: C

Explanation:

Ultraviolet (UV) radiation is a type of electromagnetic radiation that falls between visible light and X-rays in the electromagnetic spectrum. It has shorter wavelengths and higher energy than visible light. Hence, statement 1 is correct.

Prolonged exposure to UV radiation, especially UV-B and UV-A rays, can have harmful effects on the skin. It can cause sunburn, premature aging of the skin, and damage to the DNA in skin cells, increasing the risk of skin cancer. Protecting the skin from excessive UV radiation by using sunscreen, wearing protective clothing, and seeking shade is important for skin health. Hence, statement 2 is correct.

The ozone layer, which is present in the Earth's stratosphere, plays a crucial role in protecting life on Earth from excessive UV radiation. The ozone layer absorbs a significant portion of the incoming UV-B and UV-C radiation from the Sun, reducing the amount of harmful radiation reaching the Earth's surface. This protective function of the ozone layer helps safeguard against the damaging effects of UV radiation on living organisms. Hence, statement 3 is correct.

Answer: A

Explanation:

Insulin is a hormone that regulates blood sugar levels. It is produced by the pancreas, specifically by the beta cells in the islets of Langerhans. Insulin plays a crucial role in the metabolism and utilization of glucose in the body. Hence, pair 1 is correctly matched.

The pancreas is not involved in the production of thyroxine. Thyroxine, also known as T4, is a hormone produced by the thyroid gland. It is involved in regulating metabolism, growth, and development in the body. Hence, pair 2 is correctly not matched.

Glucagon is not produced by the thyroid gland. Glucagon is a hormone produced by the alpha cells of the pancreas. It acts opposite to insulin and helps increase blood sugar levels by promoting the release of stored glucose from the liver. Hence, pair 3 is correctly not matched.

Answer: A

Explanation:

According to the wave equation, the frequency (f) of a wave is inversely proportional to its wavelength (λ). This means that as the frequency increases, the wavelength decreases and vice versa. Hence, option (a) is the correct answer.