Judge the Following Sentence According to the Criteria Given Below

Judge the following sentence according to the criteria given below. The barren surface of the tidal flat exposed at low tide lacks vegetation because tidal flats form on the lagoon side of a barrier island.

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.