请教高手~

scholar

When an active tooth in the shark’s jawsis lost or worn down, many spare teeth lie in seemingly limitless reserve, eachof which are ready to slide into the appropriate position.
答案选A 我选E

1. When an     active tooth in the shark’s jaws is lost or worn down, many spare teeth     lie in seemingly limitless reserve, each of which are ready to slide into     the appropriate position.
   
   
2. Whenever     an active tooth is lost or worn down, many spare teeth lie in seemingly     limitless reserve in the shark’s jaws, which are each ready to slide into     the appropriate position.
   
   
3. Many spare     teeth lie in seemingly limitless reserve in the shark’s jaws, each one of     which are ready to slide into the appropriate position when an active     tooth is lost or worn down.
   
   
4. The many     spare teeth lying in seemingly limitless reserve in the shark’s jaws, each     one of which is ready to slide into the appropriate position whenever an     active tooth is lost or worn down.
   
   
5. In the     shark’s jaws, many spare teeth lie in seemingly limitless reserve, each     one ready to slide into the appropriate position whenever an active tooth     is lost or worn down.
   

小唯唯

这题就是选E啊？你哪看的答案啊……