______ with the size of the whole earth, the biggest ocean does not seem big at all.
| A．Compare | B．When comparing | C．Comparing | D．When compared |
— ____ in this street? — I think Mr. Black is the richest man.
| A．Whom do you think is the richest man |
| B．Who do you think is the richest man |
| C．Do you think who is the richest man |
| D．Do you think whom is the richest man |
I haven’t found my watch yet; in fact, I’m not sure ____ I could have done with it.
| A．where | B．whether | C．what | D．how |
I was advised to arrange for insurance ____ I needed medical treatment.
| A．nevertheless | B．although | C．in case | D．so that |
They were surprised that a four-year-old boy should work out such a difficult problem ____ they themselves couldn’t.
| A．once | B．then | C．while | D．if |
I think you ought to end it ____ it is too late, or you’ll kill yourself.
| A．even if | B．before | C．so that | D．once |