主要用于乳牙期、替牙期以矫正牙齿因素为主的前牙反胎的是E．
【C5】______
A. begin
B. beginning
C. begins
D. to begin
血压160-179/100～10的九次方mmHg见于E．
Futures contracts can be______.
A. used as protection against large price swings
B. countered by an offsetting purchase or sale
C. participated by hedgers or speculators
D. all of the above
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