The boy wanted to ride his bicycle in the street, but his mother told him _____.
. As a teacher, he has never given his students so difficult a problem ____ they can’t work out.
. — I don’t know ____ to join the army or to find a job. — Why don’t you ____ your parents’ advice?
. Whether ways will be found to stop pollution or not is just ____ worries the public.
. We called the First-Aid Center ____ the traffic accident happened.
. The young man always believes in ____ she says or she does because he loves her so deeply.