The old woman had a letter from her son in the army_____ to her.
Attention, please. The plane to London _______ off at 9: 00.
The Spring Festival falls ________ the first day of the Chinese Lunar year.
Do you still remember the chicken farm _____ we visited the other day?
It is diving _____ great speed that often causes serious accidents.
______ is necessary for everyone to obey the traffic rules.