Try: 1. Shortly; soon. 2. Exhausted. I think the teacher marked you wrong for the following reasons: 1. "Later" can be very much later - such as 50 years - and not in the near future. 2. "Fatigue" is not just "tiredness". It is extreme tiredness. You were on the right track, but this exercise helps you to achieve a finer understanding of the more subtle differences between similar words. So don't feel discouraged. Be happy in the knowledge that you are now ready for a higher level of the language.