1. Tiring as it might be, the military training ________ the best opportunity to make lifelong friends.
A．is believed to be B．believes as
C．is believed to being D．believes
2. A surprise attack was ________ at Pearl Harbor by the Japanese in 1941, which led to the US ________ the Second World War.
A. happened; enter B. carried out; entering
C. occurred; entering D. taken place; enter
