题目

The little boy has gift for piano and he practices it with great effort. 答案：【1】a下列各组物质以任意比混合后充分燃烧，产生的CO2分子数目一定比H2O分子数目多的是（　　）A．CH4和C2HB．H2和COC．CH4和COD．C2H4和C2H2