Very cold periods in earth's history resulted in which of the following?

A. Deposits of pollen

B. Tree rings

C. Glaciers

D. Sunspots

C.

Very cold periods in earth's history resulted in Glaciers

Explanation:

The earth experiences of cold and warm eras due to factors and phenomena such as Milankovitch cycles. On occasions, the position of the earth relative to the earth results in slightly less sunlight hitting some part so the earth - such as during aphelion when the earth is farthest from the sun in its orbit. This causes a significant drop in earth temperatures resulting in an increase in coverage of ice sheets and glaciers in the polar regions. These periods are called ice ages and the earth has had several of them in its history.