— Well, it is now. We have thirty minutes for a drink.
A:half past seven
B:a quarter past six
C:a quarter to seven
D:a quarter to six
下列各式中是二元一次方程的是( )
宋代诗人杨万里说:“诗至唐而盛,至晚唐而工。盖当时以此设科取士,士皆争竭其心思而为之。”这说明( )
____ ____ ____ ____
有甲、乙、丙、丁四位商人,分别带上自己的产品到俄罗斯参加定货会,仅考虑市场要求,请分析收到的定单最少的是( )
①NH2+CO2+X=NH4HCO3
②NH4HCO3+NaCl=NH4Cl+NaHCO3↓
③2NaHCO3 Δ__ Na2CO3+H2O+CO2↑
请回答下列问题: