2～3层扁平细胞，与釉质形成有关（）
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：D
—It’s said that Wang Meng spent almost 10 hours training every day.
—That’s true. She is really hard-working. ________, she won 3 golden medals in
the 21st Winter Olympics.
A．By the way
B．First of all
C．As a result
D．In order to
