—May I go to the theatre with you?

—I’m afraid not ____ you have a ticket, because I have only one.

A．since

B．if

C．unless

D．though

患儿男，3岁。1岁起青紫逐渐加重，哭后更严重，有昏厥史，胸骨左缘有Ⅲ级收缩期杂音，无震颤，心脏X线片呈“靴形”心影，应考虑为（）。

A.房间隔缺损

B.室间隔缺损

C.动脉导管未闭

D.大动脉转位

E.法洛四联症