---- Tom must have been in his girlfriend’s house on Christmas Eve, ________?

----- ___________．He was seeing a film all night long with us ．

A．mustn’t he；Yes ;

B．wasn’t he， No ;

C．hasn’t he；Yes;

D．didn’t he；No;

已知较完全地形成氢氧化物沉淀，溶液的pH分别为3.7．9.6．4.4左右。某硫酸锌酸性溶液中含有少量杂质离子，为除去这些离子制得纯净的硫酸锌，应加入的试剂是[ ]

A．溶液

B．

C．氨水

D．