题目

“I suppose you _____ that report yet?” “I finished it yesterday, as a matter of fact.” A. didn’t finish                                          B. haven’t finished C. hadn’t finished                                      D. wasn’t finishing   答案：B16．西瓜味甜多汁，原因是西瓜中含有大量的糖和水，这汁液主要存在于西瓜细胞的（　　）A．细胞壁B．细胞膜C．细胞核D．液泡