Answer: A) Erosion Explanation: Caverns are openings in the ground. Some famous caverns in the United States are Mammoth Cave, Carlsbad Caverns, Wind Cave, and Luray Caverns.   When rainwater trickles down through the soil, it carries carbon dioxide from the air with it. This turns acidic as it moves through the soil, joining with carbon from decaying plants. This acidic rainwater then eats away at, or erodes, the rock under the ground, forming a cave or cavern. For this process to occur, the rock must be the right type; limestone, dolomite, and gypsum are common.

Answer: A) Directive principle Explanation:

Answer: A) Sulphur dioxide Explanation: Air pollutants are solid particles, gases, and liquid droplets in the air that can adversely affect ecosystems and the health of humans.   Major ambient air pollutants include toxic metals, polycyclic aromatic hydrocarbons, benzene, particulate matter (PM), nitrogen oxides, sulfur oxides, carbon monoxide, and ozone. Power plants, factories, and vehicle and air traffic are the most important anthropogenic sources of air pollution.   In addition, natural sources such as wildfires and volcanic activity contribute to ambient air pollution.

Answer: A) It is set by multiple levels of the government. Explanation: General education policy is set by multiple levels of the government like Federal, state and local governments.

Answer: A) 416 Explanation: The given number series is  21 56 102 160 231 316   21      56       102        160      231       316         416    +35    +46       +58       +71      +85       +100         +11      +12       +13      +14      +15   Hence, the next number in the given number series is 316 + 100 = 416.

Answer: D) Agriculture Explanation: Agriculture would be a good example of a purely competitive industry.

Answer: A) CPU Explanation: Central Processing Unit (CPU) is the brain of any computer system.

Answer: C) Siva Samudram in Karnataka Explanation: Siva Samudram in Karnatka. The potential for hydroelectric power in India is one of the greatest in the world.   The first hydro-electric power station in India was established in Karnataka at "shivana samudra".