Usually a meteorological observatory (气象台) _____ air quality in urban areas from one to five: excellent, fairly good, slightly polluted, poor, and dangerous. 

Cartoons should _________ social morality and family values and avoid violent scenes, including those that children could easily imitate.

 There is one tip from the book that I do follow, and I ________ you do, too. Cut down on watching TV.

.It was so dark in the cinema that I could hardly ________ my friend. 

The topic___________ a heated discussion.