The world has a big headache and it _______ by money. It began in America last year.

Don’t stand up until you ____________.

Both teachers and students _____ not to use mobile phones in class in our school.

These English songs are very popular and they often____ on the radio all the time.

----Doctors, it seems that you like to work with animals.----Yes, I think animals should ______ as our friends.