We usually go to work _____ subway. [ ]
A. by the
B. by a
C. by
D. on
答案:C
磷酸锌粘固粉用于垫底有局限性的原因是()
A.有一定的粘结性
B.抗压强度98MPa
C.绝缘性能很优良
D.对牙髓有刺激性
E.唾液中可被溶解
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