Question

What is the main purpose of a concluding paragraph?

To add more evidence to support the thesis
To include additional questions for research
To introduce new but related information
To restate the thesis and summarize the final point

Answer 1

The answer to your question would be D. To restate the thesis and summarize the final point. 
Hope this helps and just ask if you need anything else! :)

Answer 2

The concluding sentence, well, concludes. So, it wraps all your main points up.

So, the main purpose of a concluding paragraph is to restate the thesis and summarize the final point