What is the structure labeled E in the diagram below?

The structure labeled E in the diagram is (B) Cytoplasm

Cytoplasm(b)

Explanation:

-- The theory of gravity gives a good explanation for things
that we see happening.

-- The theory of gravity predicts things that turn out to be true
when we test them.

-- Nobody has come up with a different theory that explains things better
and makes more accurate predictions that the theory of gravity does.

-- The theory of gravity can't be proved.