Judge the Following Sentence According to the Criteria Given Below

Multiple Choice

Judge the following sentence according to the criteria given below. Earth is long overdue for a magnetic reversal because during the past 15 million years Earth's magnetic field reversed every 200,000 years, on average, and the last reversal was 780,000 years ago.

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.