According to the law of conservation of matter, in any food chain we know

Matter is changed into various forms but the total quantity remains unchanged.

Explanation:

Matter in a food web moves from producers to different degrees of consumers. The producers account for the maximum amount of matter in the food web. The matter then moves higher and is consumed by the first level of consumers where some of it might remain unconsumed, undigested, or released in other forms like gas. Then the second level of consumers uses the matter available from the first level where again some matter might not move to the next level. However, never in the food web is matter created or destroyed.

b would be the right answer

one would be wind another would be water density