下列各有机化合物的系统命名正确的是( ) A．CH2===CH—CH===CH2 1,3二丁烯 B．3丁醇 C． 甲基苯酚
要将山西省大同煤田的煤炭运输到上海，最为经济合理的运输方式是（ ） A.铁路和公路运输 B.铁路和海运 C.内河和海运 D.公路运输
（08四川攀枝花）(4分)小勇同学骑着一辆自行车在乎直公路上匀速运动600m，所用时间为2min。求：(1)自行车行驶的速度。(2)若小勇和自行车总重680N，车胎
只发育成茎和叶的芽是 A．幼芽 B．枝芽 C．花芽 D．混合芽
氨水（NH3•H2O）也是常见的碱，是由NH3溶于水形成的溶液．氨水很不稳定，容易放出有刺激性气味的NH3．根据所学知识回答： （1）NH3•H2O在水溶液中解
is known to all is that good friends happiness and value to life．A．What；add to B．It；add C．What；add
Nowadays, millions of lonely singles are now going online instead, and therefore, ___33___ World Wide Web is quickly becoming the world’s most popular matchmaker(媒人). Singles are f
Why not ____ help when you were in trouble? A. you ask for B. ask for C. asking for D. to ask
