. The concert was a great success--there wasn’t a single empty seat in the concert hall, ____ it was very cold. 

“Would you mind my sitting here with you?” “No, ______ you aren’t too noisy.”

 He had to be reminded two or three times ________ he could avoid making the same mistake.

The fleet made several expeditions _______ the exploration was stopped.

—I rang you at about nine，but there was no reply．—Oh，that was probably        I was seeing the doctor．