| A report by the American Academy for the Advancement of Science has concluded that much of the currently uncontrolled dioxins to which North Americans are exposed comes from the incineration of wastes.
(A) much of the currently uncontrolled dioxins to which North Americans are exposed comes
(B) much of the currently uncontrolled dioxins that North Americans are exposed to come
(C) much of the dioxins that are currently uncontrolled and that North Americans are exposed to comes
(D) many of the dioxins that are currently uncontrolled and North Americans are exposed to come（E）
(E) many of the currently uncontrolled dioxins to which North Americans are exposed come
答案e没有问题。如果to which North Americans are exposed 改为 that North americans are exposed to可以吗？这个是定语从句吧，介词应该可以前面也可以后面，在问问：which North americans are exposed to 可以吗？ | 
