幼儿乳牙萌出过程中，恒牙还没开始发育。
参考答案：错
— Tom, you are going to buy a new flat here, aren’t you?
— Yes, but I can’t _____an expensive one.
A．spend
B．cost
C．pay
D．afford
外耳道恶性耵聍腺肿瘤约占耵聍腺肿瘤的百分率是（）。
A.90％
B.80％
C.70％
D.60％
E.50％
