Question

He feels very excited and his heart ________ very fast．

1. A.
   is striking
2. B.
   is beating
3. C.
   is hitting
4. D.
   knocks

Answer 1

B
strike, beat, hit, knock都有“敲；打”的意思。strike强调用木棒、石头等的“打”，与hit用法接近；beat侧重“连续的敲击”，如：The raining is beating against the window．beat也可以指“心脏的跳动”；knock强调“用力撞击”，如“将某人撞倒”可以说knock sb．down。