4. Few people live on the Canadian Shield because it is mostly
craggy harbors
on the Arctic coastline
exposed bedrock
rolling fields of wheat

exposed bedrock

Explanation:

The Canadian Shield is an area that exposed bedrock. Different types of rocks found in Canadian Shield are metamorphosed granite, sedimentary and igneous rocks and ancient sedimentary rocks. this is the reason few people live on the Canadian Shield. Most of the population lives in southern part of the Shield.

The Canadian shield's bare surface is much useful for industrial purpose only such as for mining and hydroelectric power generation.

Hence, the correct answer is "exposed bedrock".

answer; (d) melting of sea ice;