— should teenagers spend at least 30 minutes taking exercise?—Five times a week,according to some reports.
You’d better stop ________ .You look too tired.
My teacher encouraged me _______ more books.
-- __________ does your brother look? -- He looks __________ .
— Could you teach me how _________ cakes? — Sorry, I don’t know.
I find _______necessary to do everything we can ____________protect the environment.