介绍别人的职业时,应说:
A:I'm a student.
B:She's a student.
H2(g)+ 12 O2(g)═H2O(l)△H=﹣285kJ/mol
C3H8(g)+5O2(g)═3CO2(g)+4H2O(l)△H=﹣2220.0kJ/mol