以下哪一种口腔组织起源于外胚层的上皮组织（）
A.牙釉质
B.牙本质
C.牙骨质
D.牙髓
E.牙槽骨
参考答案：A
Parents feel they don’t have the ability to influence children’s decisions ______ children feel their parents’ goals are hard to achieve.
A．although
B．while
C．until
D．unless
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A．0B．1C．2D．3
