________ deep down in the earth,the dead forests rotted away and became coal.
—It is rather cold here. Shall we light a fire? —No, we ______because things are easy to catch fire.
It is said that his health ______ by years of hard working.
Does everyone know what to do if a fire ______?
It is obvious _________ he has known the news and he is very satisfied with the result.
We _______ in the office.