导管中侵填体形成后到第二年春天还可以溶解，导管又可恢复输导功能。( )
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厚角组织的细胞壁是在角隅处加厚，属初生的机械组织，它是生活的细胞。( )
__________ had I closed the door__________ somebody started knocking on it．
As soon as；then
B. Although；yet
C. No sooner；than
D. If；then
My calculation was wrong because I__________ One tiny point．
A. overlooked
B. ignored
C. seeped
D. leaked
From this passage，we can draw the conclusion that__________ ．
A. Kennedy’s experience of serving in the army made him a competent president
B. Kennedy’s generation and his previous generation were struck with misfortune and disgrace
C. Kennedy’s tough international policy toward Cuba had won widespread support in the country
D. For the young，being born in a wealthy and famous family may not be a blessing from heaven
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