动物细胞与植物细胞的结构不同,导致了它们有丝分裂的不同,这是因为植物细胞[ ]
A.有叶绿体和细胞壁
B.有细胞壁和液泡
C.有细胞壁,无中心体
D.有叶绿体和液泡
答案:C
I had wanted to help you last night but I couldn’t spare any time.for I_____an essay that is due this morning.
A.wrote
B.had written
C.was writing
D.have written