可见光固化复合树脂最常用的引发剂是()
A.樟脑醌
B.过氧化苯甲酰(BPO)
C.N,N-二羟乙基对甲苯胺(DHET)
D.N,N-二甲胺甲基丙烯酸乙酯
E.三丁基硼
参考答案:B
下列说法中正确的是( )
A.因为位移大小和路程不一定相等,所以位移才不等于路程
B.位移的大小等于路程,方向由起点指向终点
C.位移取决于始末位置,路程取决于实际运动路线
D.位移描述直线运动,是矢量;路程描述曲线运动,是标量
—Our P.E. teacher isn’t as young as he _______, is he?
—No, but he is one of _______ in our school.
A.looked; the youngest teacher
B.looks; the youngest teachers
C.looks; the oldest teachers
D.looked; the oldest teacher