Company law sets two as the smallest number of subscribers needed to incorporate a private company, compared with seven for a public company. The larger figures of 10 and 15 do not match any statutory member threshold for either type of company, so the number required to form a private company is 2.
We can also compare private and public company member requirements side by side to see which number belongs where.
Lining the two company types up side by side makes it clear that 2 is the figure that belongs specifically to private companies.
Therefore, the correct answer is 2.