Why do higher trophic levels in most ecosystems contain fewer organisms than lower trophic
levels?
A. Energy available for use to the highest trophic
level is small
B. Energy available for use to the lowest trophic
level is small.
C. Energy available for use to the highest trophic
level is large.
D. Energy available for use to the highest and
lowest trophic levels is the same.

A.Energy available for use to the highest trophic  level is small

Explanation:

As you go up in the trophic levels, only about 10% of the energy gets transferred from one level to the next. For example, the plants can only harvest 1% of the Sun's energy. The primary consumer can only absorb 10% of the energy from the plant he eats, so .1% of the total energy. The secondary consumer can only absorb 10% of the energy he get from eating the primary consumer, so .01%, and so on and so forth. As we climb up the trophic levels, there is less energy available and therefore less organisms.

the backbone of the dna and rna compound is sugar phosphate.

most community's take hundreds of years to become stable