Area of a regular octagon inscribed in a circle of radius 1 unit is:

This is a regular octagon (all sides of the octagon are same) inscribed in a circle.

We can solve this easily by eliminating options:

Area of circle ($r = 1$ unit) is $3.14$ units square.

Option 1 $= 2\times 1.4 = 2.8$

Option 2 $= 2 + 1.4 = 3.4$

Option 3 $= \frac{9}{2.8} = ~3.2$

Option 4 $= \sqrt{10} = 3.16$ -> (Use the calculator if needed)

Only one option is less than the circle itself (because the octagon is inscribed within it).

Hence, option 1 becomes the answer.