On Saturdays, students are very proud to be         on the street to guide passers-by to obey traffic rules.

Tom was searching hard in the classroom in the ___ of finding his lost exercise book.

The owner of the jewelry store says a(n) _______ of $ 1,000 will be offered to anyone who can find the lost jewels.

Even the experienced doctors dare not carry out the operation because of the         of failure.

If you want to get the driver’s_______ you should take some courses first in the traffic school.