With arms straight,rock forward,pressing down on the lower half of the ribs
问题描述：
With arms straight,rock forward,pressing down on the lower half of the ribs
这里rock是什么意思,如果当动词摇动讲,为什么要用动词原形形式.
答
是动词,"摆动"的意思.
是祈使句,所以动词原形.
With arms straight,和 pressing down on the lower half of the ribs是状语.