I am Puerto Rican.
Your answer should be A) Rocas.
Rocas means Rocks.
The sentence with the answer should look like this in spanish.
Las rocas son muy duras.
Translated:
Rocks are really hard.
The answer choices in English would be
A) Rocks
B) flowers
C) Insects
D) Rivers
The best answer for this sentence should be A) Rocas.