—Did you get a ticket then?

—Yes,otherwise I _________ the concert last night.

A．didn’t attend

B．wouldn’t attend

C．hadn’t attended

D．wouldn’t have attended

核酸碱基的配对原则是（）

A.A－C，T－G

B.A－T，G－C

C.C－T，A－G

D.任何两个碱基均可随意配对

E.A－T，T－G