题目

下列关于癌细胞的结构与功能的说法,正确的是 A.癌细胞为高度分化的特殊类型体细胞 B.癌细胞细胞膜两侧镶嵌的糖蛋白数量均大量减少 C.与正常细胞相比,癌细胞核糖体数量较多 D.细胞的分裂、分化、衰老、癌变对生物体均有积极意义 答案：C Jenny was very sad over the loss of the photos she had shot at Canada, ________ this was a memory she especially treasured． [　　] A．as B．if C．when D．where