[单选题]在( )内,对于关键部位及影响电网安全稳定运行的质量缺陷、因工程质量原因造成公司系统事故事件的,根据事故事件的等级按照南网公司相关管理规定分级负责开展质量责任追溯。
A.设计使用年限
B.质量保证期
C.投产后一年
D.投产后两年

From 1946 until 1954, the Vietnamese had struggled for their independence from France during the First Indochina War. At the end of this war, the country was temporarily divided into North and South Vietnam. North Vietnam came under the control of the Vietnamese Communists who had opposed France and who aimed for a unified Vietnam under Communist rule. The South was controlled by Vietnamese who had collaborated with the French.
The United States became involved in Vietnam because it believed that if all of the country fell under a Communist government, Communism would spread throughout Southeast Asia and beyond. This belief was known as the "domino (多米诺骨牌)theory." The U.S. government, therefore, supported the South Vietnamese government. This government’s policies led to rebellion in the South.
In 1965 the United States sent in troops to prevent the South Vietnamese government from collapsing. Finally, however, the United States failed to a
A. American Policy on Vietnam
B. Vietnam War
C. The Conflict Between the North and the South
D. American’s Goal