Bruce ________ at 6:15 in the morning.
A: brush his teeth
B: brushes his teeth
C: brush his tooth
D: brushes his tooth
①y︰x= 5 ②y =x ③xy =5 ④5+x =y
书写下列化学方程式:
用过氢化氢制取氧气:____
二氧化碳通入澄清石灰水中:____
利用盐酸与大理石制取二氧化碳:____
不能用铁桶盛硫酸铜溶液的原因:____ .