Tour guides for groups of over ten must be booked ______.
—Why didn't he attend the meeting yesterday?—__________ he caught a bad cold and now he is in hospital.
Many years ago, he dreamed of becoming the first person __________ both South and North Poles.
The __________ of his aim depends largely on himself.
I was about to go out __________ he came in.
The goods __________ well, so they __________ out quickly.