减水率是指掺用外加剂混凝土的用水量与不掺外加剂混凝土的用水量的比值。
参考答案：错
That car accident ____all his life. After that he was limited to a wheelchair.
A．damaged
B．destroyed
C．harmed
D．ruined
有关典型的成釉细胞瘤，下列叙述正确的是（）
A.组织发生自牙源性上皮
B.下颌前部好发
C.双侧多见
D.可形成釉质
E.生长快，早期出现症状
