The Easter offensive .

coincided with Tet
was intended to knock out the South Vietnamese government
was blunted by U. S. air attacks
was begun by U. S. and South Vietnamese forces

The Easter offensive was begun by U.S and South Vietnamese forces.

Option: D

Explanation:

Easter offensive is also known as 1972 spring summer offensive. It was literally a military campaign done by army of Vietnam. The main goal of Easter offensive was to capture South Vietnam and reunited it with North Vietnam. For this  war defense force of Vietnam struggled a lot.

In 1972 North Vietnam launched Easter offensive. North Vietnamese attacked military force of South Vietnamese by utilizing their full power. In a critical moment later U.S force helped them to stop or fight against air power.

the answers is b.   environments.

your answer would be (a)