下列哪些细胞是单倍体细胞：（）
A.精原细胞
B.卵原细胞
C.精子
D.卵细胞
参考答案：C, D
—Can you give me some advice on what I said just now?
—Sorry, my mind ________.[ ]
A. has wondered
B. had wondered
C. is wondering
D. was wondering
T2弛豫中质子横向磁化矢量时间常数是多少?
