【单选题】_______as an Olympic event, a sport must be played in at least 75 countries on at least 4 continents.
【单选题】To be elected to the Senate a person must______.
A.
be at least 25 years old
B.
be at least 30 years old
C.
have been a citizen for seven years
【单选题】The lazy boy ate the _____ food, but did the _____ work. [ ]
【单选题】湿式气缸套的冷却效果比干式气缸套的冷却效果 ( ) 。
【单选题】Which of the following does the passage mention as necessary for both the production of oxygen by photodissociation and the production of oxygen by plants?
【单选题】湿式气缸套的冷却效果比干式气缸套的冷却效果()。
【单选题】---Thank for the ride home! -----______, which of the following is wrong?