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.
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
选E。我想请教一下逗号后面的tissues not normally found in the organ in which the tumor appears在整个句子中是什么成分?是不是同位语?但我觉得同位语之间不应该互相重复的,哪位nn给我解释一下。