I can sing Chinese songs _____ I can't sing them well.[ ]
A. and
B. but
C. to
D. /
答案:B
下列各组热化学方程式中,化学反应的△H前者大于后者的是[ ]
①C(s)+O2(g)==CO2(g);△H1 C(s)+1/2O2(g)==CO(g);△H2
②S(s)+O2(g)==SO2(g);△H3 S(g)+O2(g)==SO2(g);△H4
③H2(s)+1/2O2(g)==H2O(l);△H5 2H2(g)+O2(g)==2H2O(l);△H6
④CaCO3(s)==CaO(s)+CO2(g);△H7 CaO(s)+H2O(l)==Ca(OH)2(s);△H8
A.①
B.④
C.②③④
D.①②③
斜导柱分型与抽芯机构中()的结构,不需要有定距分型机构。
A.斜导柱在动模,滑块在定模
B.斜导柱在定模,滑块在动模
C.斜导柱与滑块同在定模
D.斜导柱与滑块同在动模