active gas活性气体activeadj.活跃的；积极的；起作用的；灵活的active ginseng capsule活性人参胶囊active fire precaution主动防火active homing guidance主动寻的制导active biological film活性生物膜Active frequency drift主动移频active aluminium oxide活性氧化铝Active Air Target Fuse空中目标主动式引信active marketing model主动营销模式active snubber circuit有源缓冲电路active atoms of carbon活性碳原子

1. It's very difficult to climb a sheer cliff.
   攀登陡峭的悬崖是很困难的。
2. The waves had undermined the cliff.
   波浪冲刷侵蚀悬崖的底部。