We will have a picnic ________ it doesn’t rain tomorrow.
Leo was late for class again. So he____ clean the classroom after school.
His wife advised him________ drinking, but he wouldn't.
That beautiful skirt is _____ cotton.
— Why _____ most stars _____ in the daytime? — Because the sun is too bright.
— Students _____ be allowed to use mobile phones at school. — I agree. Phones can bring troubles.