41. If you don’t advance, you would be behind _____.
_______, the more exercise you do, the richer your knowledge will be.
His mother happened _______ when his program was shown on Channel Young.
By the time he was ten, Edison _________ experiments in chemistry.
The businessperson wanted to sell his goods fast; ______, he chose his partner with great care.
Do you know the man____ is talking with Tom?