im pretty sure the answer is going to most likely be A: decomposing dead plants and animals
A good index fossil is one with four characteristics: it is distinctive, widespread, abundant, and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms
The answer is D its tightly packed cells allow for proctection against harmful substances.
This is referring to meiosis, which happens just once to make reproductive cells, unlike mitosis which is just simple copying.
In mitosis, one cell splits into two, but the number of chromosomes doesn't change. The original cell makes two copies of its chromosomes and divides them up.

In <em>meiosis</em>, however, our cell doesn't bother making those two copies. It just takes what it has and divides it between two new cells.