求教过去分词 现在分词 以及定语从句的用法

张小7

在此附一道题  33. GWD17-Q33:

Doctors hope that one day the body’s master cells, called stem cells, can be directed to grow in organs or tissues appropriate for transplant, use them to test drugs and potentially toxic chemicals, and may study them to gain insight into basic human biology.

1. transplant, use them to test drugs and potentially toxic chemicals, and may study them
   
   
2. transplant, using them to test drugs and potentially toxic chemicals, and studied
   
   
3. transplant, used to test drugs and potentially toxic chemicals, and studied
   
   
4. a transplant, use them for testing drugs and potentially toxic chemicals, and for studying
   
   
5. a transplant, used to test drugs and potentially toxic chemicals, and may study them
   
   

张小7

顶一下 有时候做题只能凭语感，因为有很多  逗号+过去分词 or逗号+现在分词 之类的