This area has been free from Foot-and-Mouth Disease ______ two years．

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This area has been free from Foot-and-Mouth Disease ______ two years．
A.for
B.in
C.after
D.before

本题关键词:T管,t-PA,T形,T波,T株,头颅T,S-T段,RAEB-t症,T形管,T蛋白;