because of vs in that

[kiranlegend]

Teratomas are unusual forms of cancer because thev 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

the answer is E. why is E preferred over A? what is the difference between because and in that? also why is D incorrect? is it because of the dangling modifier 'tissues such as tooth and bone'?

[kiranlegend]

i understood that Because is used when there is a causal relationship.. whereas in that is used to tell the way the discussing subject is different.. is it correct?