A:工业用水应该循环利用
B:生活污水直接排放不会造成水污染
C:喷灌、滴灌可以减少大量用水
D:水被严重污染后会给人类带来灾难
____ ____,I went to the library by taxi.
①2C2H2(g)+5O2(g)═4CO2(g)+2H2O( l )△H1=﹣2602.0kJ•mol﹣1
②C(s)+O2(g)═CO2( g )△H2=﹣393.5kJ•mol﹣1
③H2(g)+ 12 O2(g)═H2O( l )△H3=﹣285.8kJ•mol﹣1
则反应④2C(s)+H2(g)═C2H2( g )的△H为____.
____ ____ ____it stopped raining ____he went out.