问题
选择题
— What color are the cats?
— I think _____ white and black. [ ]
A. they're
B. them
C. it's
D. it
答案
答案：A
搜题请搜索小程序“爱下问搜题”
— What color are the cats?
— I think _____ white and black. [ ]
A. they're
B. them
C. it's
D. it
答案：A
，分别在U形管两端小心倒入饱和食盐水和饱和稀硫酸溶液，并使a、b两处液面相平，然后分别塞上插有生铁丝的塞子，密封好，放置一段时间后，下列有关叙述错误的是
