Judge the Following Sentence According to the Criteria Given Below

Judge the following sentence according to the criteria given below. Ground water moves along the top of the water table from high elevation to low elevation because the slope of the water table determines the direction of ground-water flow.

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