眼表的范围是指（）
A.泪腺
B.结膜上皮
C.角膜上皮
D.泪小管
E.泪膜
参考答案：B, C, E
She reached the top of the hill and stopped _______ on a big rock by the side of the path. [ ]
A. to have rested
B. resting
C. to rest
D. rest
下列不属于转基因牛的培育步骤的是（ ）
A．细胞核移植
B．体外受精
C．胚胎移植
D．导入外源基因
