I think it is erosion (2) because erosion removes soil, rock, and dissolved material.
I don't understand, what is the question you're supposed to answer?
Answer: C
Explanation: Left ventricle. With the thickest muscle mass of all the chambers, the left ventricle is the hardest pumping part of the heart, as it pumps blood that flows to the heart and rest of the body other than the lungs.