长期卧床的心力衰竭病人，发生下肢血栓脱落可引起哪一部位栓塞()
A．脑
B．肾
C．肺
D．脾
E．四肢
参考答案：C
All possible means ____ to prevent the air pollution, but the sky is still not clear.
A．is used
B．has been used
C．are use
D．have been used
．Joining us in the program today __________Mr. Smith, together with his wife. Welcome to our program.
A．was
B．are
C．is
D．were
