— I haven't heard ______ Peter yet.
— Don't worry. No news is good news. His letter will arrive soon.
A:of
B:from
C:to
图形在平移和旋转后,____发生了变化,____不变。图形在放大与缩小后,____发生了变化,____不变。
当转动显微镜的粗准焦螺旋,使镜筒缓缓下降时,操作者的眼腈一定要看着( )