— Oh, must you? Stay a bit longer. It has been such _____ fun having you here.

— Thanks. I've got _____ early start tomorrow morning. [ ]

A. a; an

B. /; the

C. /; an

D. the; an

设f（x）=（1+e）／（2+e），则x=0是f（x）的：（）

A.可去间断点

B.跳跃间断点

C.无穷间断点

D.振荡间断点