The correct answer is true.
It is true that the Viet Minh destroyed the main airstrip at Dien Bien Phu.
We are talking about the Battle of Dien Bien Phu, during the First Indochina War, between the French troops and the Revolutionary forces of the Viet Minh. The armed confrontation started in March 1954 and ended two months later on May 1954. The Communist Vietnamese troops outsmarted the Frenchs, surrounded their camp, dig tunnels carried heavy artillery and took the French camp.