I was shocked to see my friend lying at the edge of the road.

The correct answer is A. side.

The other options are incorrect because:

• B. bank is the land alongside a river or lake.
• C. corner is the point at which two or more lines or edges meet.
• D. border is a line that separates two countries or regions.

In the sentence “I was shocked to see my friend lying at the edge of the road,” the word “edge” refers to the boundary between the road and the area next to it. This area is typically called the “side of the road.”