_____is known to us all is that the old scientist, for____ life was hard in the past,still works very hard in his eighties.
---Any advice for me? ---You’d better the timetable to see when the train leaves.
If traffic moves at low speeds, the number of accidents is.
—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
---Do you mind if I keep pets in this building? --- _________.
---How bright the sun is! ---You’d better wear your dark glasses to_____ your eyes from it.