It remains __________ whether the medicine will work on the human body.
________ that I was puzzled.
The factory, including its machines and buildings, ______ burnt to ashes during the fire.
– Are you cleaning my room? – I can’t help _____.I can’t bear seeing people’s room in a mess!
He thought that painting copied by a modern artist was ______ great value and bought it ____ over a thousand dollars.
Let him who tied the bell onto the tiger take it off -- _____ started the trouble should end it.