通过细胞核移植实验可以证明，生物的遗传信息中心是 [ ]
A．细胞壁
B．细胞膜
C．细胞核
D．细胞质
答案：C
Peter had intended to take a job in business, but ________ that plan after the unpleasant experience in
Canada in 2010.[ ]
A. had abandoned
B. abandoned
C. abandon
D. will abandon
已知x2-2x-3=0，那么代数式2x2-4x-5的值是______．
