Asource from which organisms generally take elements is called a/an
a. biotic community.
b. reservoir.
c. exchange pool.
d. food web.

C. Exchange pool.

Explanation:

The exchange pool can be define as the pool which includes the elements which are required to be exchanged between the abiotic and biotic components of the environment. This is the part of every biochemical cycle.

On the basis of the above explanation, an exchange pool is the source from which the organisms generally take elements so as to lead their life cycle. For example, the atmosphere is the exchange pool of gaseous elements such as water vapors, oxygen, carbon dioxide and nitrogen. The organisms take oxygen from the atmosphere for respiration and release out carbon dioxide which becomes the part of the atmosphere.

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force