The students stopped ________ when the teacher came in.
A:talk
B:to talk
C:talking
D:talked
如图,在等腰Rt△ABC中,AC=BC=2 2 ,点P在以斜边AB为直径的半圆上,M为PC的中点.当点P沿半圆从点A运动至点B时,点M运动的路径长是( )