With the help of the smart phones, you ____ video chat with your friends on the phone.

The child is only 4 years old, he is not old enough to___ himself.

I was leaving the office when it suddenly 　　　 to me that I had forgotten my keys.

Is David honest and organized boy?— Yes, that is why he was chosen to be the president of the Students’ Union.

_________ is said that most teenagers have problems such as Li Ming’s.