海南三亚一中月考3，24）So difficult _______it to work out the problem that I decided to ask Tom for some advice.

A．I did find

B．did I find

C．I’ve found

D．have I found

扣拳又称掸扣拳或兜弓拳，练习时应注意，反手掸扣时以肘关节为运动软骨头的心朝上或朝下，力击点达于（）。