求教OG10-SC208题

208. Teratomas are unusual forms of cancer because they are composed of tissues such as tooth and bone not
normally found in the organ in which the tumor appears.
(A) because they are composed of tissues such as tooth and bone
(B) because they are composed of tissues like tooth and bone that are
(C) because they are composed of tissues, like tooth and bone, tissues
(D) in that their composition, tissues such as tooth and bone, is
(E) in that they are composed of tissues such as tooth and bone, tissues

ABCD我已经都可以排除，但对于答案E还有点困惑。in that在这里让我怎么看怎么不爽。in that是否可以换成in which? 我怎么记得that引从句时不可以把介词提前呢？

求高人赐教！不胜感激

in that here means because.. i see..i forgot the phrase

thanks all the same.