The answer is B) metaphase
In complementary base pairing, the G pairs with C, and A pairs with T. Given that this be the rule, the complementary nucleotides for your sequence would be as follows: CGATTAACGTAGGCA.
With regards to proofreading, mutations in cell division occur once in around every 100,000 base pairs. If this happens, the enzyme that pairs the nucleotides to form DNA, called DNA polymerase, detects the error and moves back along the strand, it then cuts the incorrect nucleotide and replaces it with the correct one, fixing the error and continuing with the DNA synthesis.
This process corrects the majority of errors in DNA synthesis, but some errors can still be missed by the DNA polymerase, this is then rectified by a protein complex which binds to the incorrect pairing until anther complex, comes along and cuts that particular section of DNA out, which is then replaced by a new section of correct nucleotides synthesized by the polymerase enzyme, the two sections at either end that were cut is then sealed by ligase, an enzyme which essentially "glues" the DNA stands back together.
My apologies for the long answer, I hope I answered your question and that you understand it well enough.
I'm almost sure your answer is going to be "Because the sun's mass creates a gravitational force that pulls earth towards it."
correct me if I am wrong.
