can, could, should, ought to,may, might,

Tom must tidy his office today because he cannot find anything anymore. His boss tells him that he ought to be tidier. Otherwise he cannot work in his department anymore. When customers want information, he should be able to help them immediately. He must not keep them waiting. If he sorts the files now, he need not panic when a customer calls. Instead, he can help them immediately.

Tom must tidy his office today because he cannot find anything anymore. His boss tells him that he ought to be tidier. Otherwise he cannot work in his department anymore. When customers want information, he should be able to help them immediately. He must not keep them waiting. If he sorts the files now, he need not panic when a customer calls. Instead, he can help them immediately.