Question

On this Vietnamese holiday, the Viet Cong attacked 27 U.S. and South Vietnamese bases at once A. Confucius' birthday
B. Tet, Vietnamese New Year
C. Trung Nguyen, Day of the Wandering Souls
D. Trung Thu, autumn celebration

Answer 1

The operations are referred to as the Tet Offensive because there was a prior agreement to "cease fire" during the Tet Lunar New Year celebrations. Both North and South Vietnam announced on national radio broadcasts that there would be a two-day cease-fire during the holiday. Nonetheless, the Communists launched an attack that began during the early morning hours of 30 January 1968, the first day of Tet.
http://en.wikipedia.org/wiki/Tet_Offensive
So your answer would be B.