Answer: A.) We have 20 days max to finish the project.
Explanation for why the other choices are incorrect:
For B: "Who is up for" is not the proper phrase to be used. It should say "He is is the type of person to most likely..." or something similar.
For C: What thing? It needs to be more specific.
For D: "They ought" is not correct and should be "They should" or something along the lines of that.