After the amateur singer competed in the program The Voice of China, his singing career   .      

If you cannot come to the meeting, please let us know ______ so that we will cancel your hotel booking.

Without my glasses, I couldn’t _____ whether that figure on the blackboard was a three or an eight.

David is into football, and he wonders how much time it ______ to be a good footballer.

Many wage earners in big cities find they may only have enough to ____ their houses, cars and other costs of living and have little extra money to invest.