The correct answer is:
A) Changes in the earth climate-caused ice sheets to grow.
Explanation:
The Antarctic Ice Sheets grew to the continental shelf break that had been extended with the continental ice sheets covered much of Canada, the northern United States, northern Europe, and extended into the Arctic Ocean. Ice sheets responded to the change in both the precipitation (snow) and the summer temperature with cold, wet conditions favors the growth of the ice and dry and warm conditions retreat the ice. This is how the Changes in the earth climate-caused ice sheets to grow and caused virtually all Canada and some of northern US to be once covered by thick glacial ice. They also faced the glacial-interglacial cycle.
