用组织培养技术繁殖时，不可能发生的是（）
A.基因重组
B.基因突变
C.染色体变异
D.染色体分离
参考答案：A
When I said that someone was late for the meeting, I________you.Why were you so angry at that time?[ ]
A. didn't refer to
B. wasn't referring to
C. haven't referred to
D. hadn't referred to
目前临床上常用的超声波剂量为（）。
A、1~3.5W/cm²
B、0.5~3.5W/cm²
C、0.5~3W/cm²
D、0.1~3W/cm²
E、0.1~3W/cm²
