变一般疑问句、针对画线部分题问请将This blue dress isn't mine.This lovely vase
变一般疑问句、针对画线部分题问 请将 This blue dress isn't mine. This lovely vase belongs to my sister.变一般疑问句 These letters are theirs.对theirs提问 The doctor says he will come at once.对he will come at once提问
Isn't this blue dress yours?/Is this blue dress not yours? Does this lovely vase belong to your sister? Whose are these letters? What does the doctor say?