2. That dictionary belongs to the library.
3. It must be him who stole the keys.
4. Lijun caught up with other students with the teacher’s help.
5. He had an accident last week.
註解：1,3句都是屬於情態動詞用在推測句中的用法；第壹句的because 是根據句意需要加上去的。
第三句我用的強調句式：It is…who…強調偷鑰匙的人是“他”。
第四句“李軍趕上了…”妳打錯壹個字。
趕上: catch up with.
在…的幫助下：with sb’s help