I heard that you made a bicycle trip to the 2010 World Expo of Shanghai alone. — No. Actually, my friend Bob ______ me. [ ]

Have you heard of such an experiment ________ wine experts were fooled into thinking a cheap bottle of wine was an exceptional one with the labels changed.

People who exercise _____ are less likely to feel stress [ ]

If it had not been for your help, I ____ the examination.

Sam remembered several occasions in the past ____ he had experienced a similar feeling[ ]