求助一道JJ的语法题，鲨鱼牙齿each of which are的那个

forestream

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. 据说答案选A
A. 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.  
B. 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. （which指代不清）
C. 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.
D. 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.
E. In the shark’s jaws, many spare teeth lie in seemingly limitless reserve, each one ready to slide into the appropriate position whenever an act tooth is lost or worn down.

昨天看JJ看到这个脑子就down了（这道据说是GWD原题不过我没做过GWD），想问A的each of which are。。。也没问题吗？挣扎了5分钟了这题……-------------
原来据说的答案是搞错了……汗，大家跳过此贴哈！

forestream

哈哈，谢谢楼上的，我本来选E的，所以死活不明白A为什么能对。刚才看到更新的JJ，发现原来是答案搞错。