I suppose by the time I come back next year, all these old houses south of the Baoshehe River ________ down.

A．will have been pulled

B．will be pulling

C．will have pulled

D．will be pulled

社区干预试验中，下列哪条不是它的缺点（）.

A.对研究对象的有关条件控制过严

B.采用随机分组很难控制混杂因素

C.设计与实施比较复杂

D.研究人群的依从性较差

E.容易引起医德和伦理学的争议