请教逻辑反应不过来怎么办

12. Mercury, one of the deadliest toxins, makes up approximately fifty percent of the amalgam used by dentists in sliver fillings. The effects of acute mercury poisoning are known-kidney failure, muscle tremors, memory loss, and even death. It is clear that responsible dentists should remove all of the patients silver fillings and replace then with filling of plastic composites.     Which of the following, if true, most strengthens the author's argument?
(A) Sliver fillings gradually corrode and small amounts of mercury leak from the amalgam.
(B) It is difficult to measure the amount of mercury in a person's body.
(C) Some patients have more than one filling per tooth.
(D) Mercury poisoning produces a range of subtle but distinctive symptoms.
(E) The materials for plastic composite fillings are readily available to dentists.

这题答案是A，我选的是E。我当时就感觉没有一个是对的。后来，发现凡是这样的加强，我基本上全错。

这可怎么办啊？

谢谢。