Judge the Following Sentence According to the Criteria Given Below

Multiple Choice

Judge the following sentence according to the criteria given below. Seafloor elevations decrease away from mid-ocean ridges because cooling lithosphere contracts, becomes denser and sinks down into the weak asthenosphere.

A) The assertion is correct but the reason is incorrect.
B) The assertion is incorrect but the reason is correct.
C) The assertion and the reason are both correct, and the reason is valid.
D) The assertion and the reason are both correct, but the reason is invalid.
E) Both the assertion and the reason are incorrect.