下列关于要约生效时间的表述正确的是( )
A.要约人寄出要约时
B.受要约人理解要约内容时
C.要约到达受要约人时
D.受要约人对要约内容准备答复时
参考答案:C
Does your mother teach you English? Yes, ____________.[ ]
A. he does
B. she doesn't
C. she does
双极集成电路中的晶体管工作机理依赖于电子或者空穴。