1. I hard, so I felt very tired.
a) had worked - if you want to emphasise that the job had been finished before you felt tired
c) had been working - if you want to say that performing some work made you tired
2. I my money into real estate.
b) have invested - if you mean that it's going give you profits
a) invested - if it happened some time ago and there's no connections to present situations
3. We alreadythe goods when your telegram arrived.
b) had shipped
4. The invoice by the end of the week so we sent them a strong reminder.
c) hadn't arrived
5. I nothing on the Internet this month.
a) have bought
6. This strategy seems to be good. Sales of our products for some time.
b) have been increasing
people can feel many things when they make music. It all depends on the nature and genre of music. you can feel, joy, fear, fun, fatigue, and so on. also it all depends on the composer himself