First of all, this isn't Geography. Second of all, look around Brainly for the answer before you post a question, because it has been answered over 10 times now...
Answer:
That is much less often than in the last 150 million years, when the field has flipped every 600,000 years. In the last 10-20 million years it has sped up even more, to once every 200,000-250,000 years. "The evidence points to a more stable field in the very far past and fewer reversals," says Veikkolainen.
B.the centerpoint formed by low pressure
