接触镜配戴者睡眠时角膜氧供主要来源于()。
A.大气
B.球结膜
C.角巩膜缘血管
D.接触镜
E.房水
参考答案:C
—Tom, you never told me why you were late for school again,_____ you?
—____. But maybe you forgot it, sir.
A.weren’t, No
B.did, No
C.did, Yes
D.didn’t, No
可遗传变异和非遗传变异其区别在于前者在任何环境下都表现相同的表现型。