The correct answer is A. milder, and precipitation
Explanation:
According to grammar, when two or more sentences are independent and have the same importance they can be link either using a semicolon (;) or one comma (,) followed by one coordinating conjunction that includes the words but, so, yet, nor, or, and. The sentences presented "Coastal areas of the Antarctic are milder" and "Precipitation in those regions averages up to eight inches per year" are both complete and independent sentence and therefore can only be combined using only a semicolon or the comma followed by the conjunction. Therefore, the only correct option to combine these two sentence is "milder, and precipitation".
They grow suspicious of each other, afraid that one will cheat the other out of a win. They decide to treat each other as purely competitors for the time being.
"As if" implies that it is not like any other day. This statement builds suspense by telling the reader that something important and out of the ordinary is going to happen.