— I hear the famous singer Xu Song may come to Ningbo next month.

— Really? _______ he comes, my younger sister will be very excited.

A．If

B．Until

C．Unless

D．Before

断指再植的冷缺血时间可长达多久后仍可再植成功（）

A.12小时

B.30小时

C.48小时

D.56小时

E.100小时