Hi vusal808.
Since the assumption has to fill a gap in the argument, maybe it will help for you to get better at identifying gaps.
A great way to see the gaps very clearly is to ask yourself what the difference is between the evidence and the conclusion. For example, consider the following argument from the TTP course:
MowGreen, a company that uses sustainable methods to maintain lawns, has been expanding quickly, and its services are now available in many areas of the country. However, given the state of the economy in the Drawnville area, MowGreen would not be able to operate profitably there. Therefore, one can be sure that MowGreen will not expand its operations into the Drawnville area any time soon.
Notice the difference between the evidence and the conclusion.
The evidence is "MowGreen would not be able to operate profitably there."
The conclusion is "MowGreen will not expand its operations into the Drawnville area."
So, the evidence is about profitability whereas the conclusion is about expanding operations. The argument has jumped from one to the other. So, the correct answer will connect those two things.
For some other insights that could help Assumption questions click for you, see the following video.