8. He is optimistic. Even though he has ______ all the difficulties, he never gives up hope. (A) encountered (B) translated (C) appreciated (D) competed

10. The dirty air, known as smog, is a combination of weather conditions, fumes and smoke from cars and factories and therefore is sure to ______ many serious health problems. (A) bring up (B) give rise to (C) look forward to (D) have little to do with