In chemistry rusting is called as oxidation. Oxidation is a chemical process where metal gains oxygen and become oxide. In rusting the Iron ore make a chemical reaction with the oxygen in the presence of water and environmental or atmospheric moisture to produce an Iron oxide. Iron oxide is otherwise called as rust. The rusting of iron is a chemical change because it is two substances reacting together to make a new substance.    Rusting would only be a physical change if iron molecules remained pure iron throughout the process.

Answer: A) R correctly explains A Explanation: Most Himalayan rivers are perennial because they are fed by the melting snow throughout the year.Thus, both A and R are true & R correctly explains A.

Answer: D) a person who balances social, physical, and mental health Explanation: A person who balances all the three healths such as Physical, mental and Social healths has the best overall health.

Answer: A) 23 Explanation: Total number of female members = 115 Let the number of males = x Number of females = y => x + y = 115  ......(1) According to the given data, x + y(0.50) = 69 ......(2) From (1) & (2), we get 0.5y = 46 => y = 46 x 2 = 92 => x = 115 - 92 = 23   Hence, required number of gentlemen in the family = x = 23.

Answer: D) Can't determine Explanation: NUMERICAL has 9 positions in which 2, 4, 6, 8 are even positions. And it contains 5 consonents i.e, N, M, R, C & L. Hence this cannot be done as 5 letters cannot be placed in 4 positions. Therefore, Can't be determined.

Answer: B) rock color Explanation: Except Rock color, all other Graded bedding, Ripple marks and Mud cracks are sedimentary structures.

Answer: D) A wildlife management agency Explanation: A wildlife management agency sets hunting regulations in most states.     These agencies will have regular meetings where the public can voice their concerns and make suggestions. Hunters wishing to propose changes to the regulations should participate in these meetings or join a hunting organization that interacts with the agency.

Answer: A) the fittest organisms survive and reproduce Explanation: Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.