A:What’s u
B:Who does he think he i
C:Does he have anyone in mind
D:Does he have anything on his mind
关于x的方程(a -5)x²-4x-1=0有实数根,则a满足( )
①浓硫酸和浓盐酸在空气中敞口放置时浓度均减小
②浓硫酸能在白纸上写字,氢氟酸能在玻璃上刻字
③二氧化硫能使品红溶液、溴水褪色
④氨气和碘化氢气体均不能用浓硫酸干燥
⑤常温下浓硫酸用铁的容器存放、加热条件下浓硫酸能与木炭反应( )