Ok, DNA Polymerase is an enzyme that joins free nucleotides to both existing strands of DNA, which means it isn't D (which is helicase, by the way). They normally work in pairs of two for this function, so it isn't C; this is because if it created a fork, there would only be one needed. Now, concerning A & B, you'll have to be careful. Depending on how A is worded contextually, it could be correct, or it could not. I'm not sure I like the wording "chunks." Which is why I think it's B. Polymerase joins one strand of the "unzipped" DNA to free nucleotides that match it, and these aren't "chunks of DNA." Now, Polymerase is VERY accurate, only making a mistake once every millionth (or billionth?) nucleotide matchup. When it does make a mistake (most of the time), it'll go back and fix it. So I believe the best answer is B, it checks for errors.
Hope this helps!
I believe the answer is photon
A process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction.
Answer: Louis Pasteur
Louis Pasteur in 1860s, proposed germ theory. The theory was based upon the fact that diseases are caused by the microorganisms. He was officially the first to publish his work.