A mountain chain extends nearly 800 miles (1,290 km) from North to South Vietnam. How do you think this terrain aided the Vietnamese guerrillas who were fighting U.S. troops?

A: This terrain aided the Vietanamese guerrillas who were fighting U.S. troops by enabling them to blend into the evironment that U.S. troops were not familiar with.

2 answers

REVISION:

This terrain aided the Vietnamese guerrillas who were fighting U.S. troops by enabling them to blend into the environment of the mountains that U.S. troops were not familiar with.
This is an adequate response.