A:121÷7
B:121÷4
C:192÷6
D:610÷2
——The little girl often has nothing for breakfast, ________she?——_______. Because she often gets up late and is afraid of being late for school.
在2H2+O2点燃2H2O的反应中,H2、O2、H2O的质量比为____,若要生成27 g水,需要____g氧气和____g氢气才能恰好完全反应。