I am sorry I ______ your glass off the desk when I was wiping it.

【正确答案】 D

【答案解析】 drew off脱去，放掉；hit off适合，将打掉；struck off砍掉，击断；knocked off撞倒。句意为：对不起，我擦桌子的时候碰掉了你的杯子。