下列具有屈光作用的是()
A.虹膜
B.房水
C.睫状体
D.脉络膜
E.视网膜
参考答案:B
Steve was busy clearing the cups and dishes from the table ________ others were playing.
A.until
B.if
C.since
D.while
建立生理系统数学模型的方法主要包括()和()。