I ______ Mr. Smith since he moved to Shanghai.
A:didn't hear from
B:don't hear from
C:haven't heard from
D:won't hear from
正常情况下在用显微镜观察时,眼睛和镜筒的相关位置应该是如图的( )
①υ(A)=0.5mol•L﹣1•S﹣1②υ(B)=0.3mol•L﹣1•S﹣1
③υ(C)=0.8mol•L﹣1•S﹣1④υ(D)=1mol•L﹣1•S﹣1.
下列有关文学常识的表述错误的一项是( )