—How did it _____ that you made such a silly mistake?
—I myself haven’t figured it out yet.

Considering the advantages of the method, they decided to         it.

Though John and David are twins, yet they differ widely _______ character.

I ________ an old friend in the street the other day whose changes surprised me a lot.

In my opinion, it's the flying birds rather than the pilot that________for the air crash.

I’ve got to go now. Something has just _________ at school and I’m needed there.

The Australian boy has a good _____ of Chinese and can communicate with others freely.

Children are ____ to meet with setbacks as they grow up, so their parents don’t have to worry about it．

As a famous public figure, you have a duty to _________ yourself responsibly, especially in public places.