一层立方上皮，借牙板与口腔上皮相连（）
A.外釉上皮层
B.内釉上皮层
C.星网状层
D.中间层
E.釉结
参考答案：A
— Would you like to go and see the film with me this evening?
— I am sorry, I can't because I _____ my homework. [ ]
A. does
B. did
C. am doing
D. has done
调质调质
