4的平方根是( )
A:-2
B:2
C:±2
D:±2
②2H2(g)+SO2(g)═S(g)+2H2O(g)△H=+90.4kJ/mol
③2H2(g)+CO(g)═CH3OH(g)△H=﹣90.8kJ/mol
请回答: