The school bus was _________ by thick fog.
30. It looks ______ you are ill. You should go to see the doctor.
29. Please ______ your sister to bring the ticket for the concert.
28. Be careful! The slightest spark(火花)could ______ the fireworks.
27. The police are offering a $ 60,000 _____ for information about the killer.
26. People generally think that smoking is a bad ______ .