语法问题一个~~~应该比较简单，但是我有点糊涂。。

空格空格

[size=14.399999618530273px]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.

• Atransplant, use them to test drugs and potentially toxic chemicals, and may study them
• Btransplant, using them to test drugs and potentially toxic chemicals, and studied
• Ctransplant, used to test drugs and potentially toxic chemicals, and studied
• Da transplant, use them for testing drugs and potentially toxic chemicals, and for studying
• Ea transplant, used to test drugs and potentially toxic chemicals, and may study them
  

B选项中them指代不清的状况是不是因为them前面有很多复数的名词，哪一个都可以被指代所以有歧义？

skyemotion

选项B逻辑不清楚。
Doctors hopes..that...cells..using.
成了cells use。