—Is that an eraser?
—No, ______.[ ]
A. it is
B. it isn't
C. that isn't
答案:B
溞类活动抑制试验的试验结果应求出24h和48h的EC50,并计算95%的置信限。
下列曲线表示减数分裂过程中DNA含量变化的是()
A B C D
A.A
B.B
C.C
D.D