1. Look, there is a bird _____ (sing) in the tree. 2. The bad air makes my chest hurt and it"s difficult for me _____ (breath). 3. They are doing their homework carefully. You"d better not _____ (disturb) them. 4. Litter _____ (influence) the look of our city. 5. It is known that smoking does great _____ (harm) to us. |