CxHy + (x+y/4)O2 == xCO2 + y/2H2O
1mol烃燃烧消耗氧气为(x+y/4)mol
①C2H6 2+6/4=3.5mol
②C2H4 2+4/4=3mol
③C2H5OH看成C2H4·H2O,和C2H4一样3mol
④C2H2 2+2/4=2.5mol
⑤C6H6 6+6/4=7.5mol
所以选 A②③