Although it was his first experience as chairman, be ________ over the meeting with great skill.
A. presided
B. administered
C. mastered
D. executed
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The ________ from childhood to adulthood is always critical time for everybody.
A. conversion
B. transition
C. turnover
D. transformation
_______ efforts are needed in order to finish important but unpleasant tasks.
A. consecutive
B. condensed
C. perpetual
D. persistent
滚子式从动杆的滚子____选用的过大,将会使运动规律“失真”。