问两道道反义疑问句1.U needn't tell her the news,_____?A don't U B do

问两道道反义疑问句
1.U needn't tell her the news,_____?
A don't U B do U C needn't U D need U
还有顺便说一下为什么选这个答案.我分不清到底是不是情态动词可以直接反问?
2.U left your wallet._________
A So did I B So I did
这一句句子,如果上下两句为同一个人说的,选哪个?
如果前一句句子是A说的,后一句句子是B说的,选哪个..?这个我也老分不清..