某医生在某地区观察饮水除氟预防氟斑牙的效果，该试验属（）.
A.社区试验
B.临床试验
C.现场试验
D.诊断试验
E.治疗试验
参考答案：A
-----The old man wouldn’t stay at home for a rest even if it rained.
---- . He would feel sick if he stayed home for one day.
A．So would my grandpa
B．So wouldn’t my grandpa
C．Neither would my grandpa
D．Nor wouldn’t my grandpa
装有液压助力的汽车为什么不能使方向盘保持在极限转向位置？
