Thank you for the trouble you have ____ to help me.
—— I would never trust him again. He let me down. —— ________.
John is the only one of the students in the class that never _______ a mistake even when it is pointed to him.
—— What do you suggest? —— My suggestion is that Andrew ________ abroad and he stay there until the project completes.
Mr. Li was out of touch last week. The police ________ for him since.
The cigarette end ________ by a careless woodcutter ________ the big forest fire.