| 1 | I'm not sure whether he will come today. | |
| 2 | This much is certain, you will never walk again. | |
| 3 | I will definitely be back before five o'clock. | |
| 4 | I am not certain I have grasped what you meant. Is it(that) you are not satisfy with your present job? | |
| 5 | I never knew whether he was afraid being with me would guarantee her a grilling by the KGB, or he just thought I was unworthy of his sister. |
