题目

 The alarm was first gone off on the third floor.                                         1.        People left the building hurriedly but in a orderly manner.                                    2.        They came out carry their shopping bags and their parcels，                           3.        some not properly wrapped and some not even paid.                                     4.        Most passer by waited in the str有3个热化方程式：H2（g）+1/2O2（g）=H2O（g）；△H ="a" kJ/molH2（g）+1/2O2（g）=H2O（l）；△H =bkJ/mol2H2（g）+O2（g）=2H2O（l）；△H =ckJ/mol关于它们的下列表述正确的是（  ）A．a+b＝c B．1mol H2O由气态变为液态吸收（a-b）kJ热量C．氢气的燃烧热为c/2 kJD．1molH2 O由液态变为气态吸收l c/2-al kJ热量