To my mind, the secret to happiness__________ your successful work and your contribution towards others’ happiness.
Many kindhearted people ___________ the Disaster Relief Fund to help the people in the earthquakestricken area.
In order to improve English,_______________.
—Why did you go to the wrong office? —Well, I forgot which room I was __________ to go to.
He was observed __________ into the house and help himself to what he liked before the owner came back.
Hospital staff burst into cheers after doctors completed a 20-hour operation to have_______ one- year-old twins at the head.