Explanation:

- Let's assume A completes a unit of work in 'x' days.

- B is 200% more efficient than A. This means B does work in (1/3)x days.

- C is 50% more efficient than B. So, C does work in (2/3)x days.

- Together, in 2 days, they do the work equation is: (2/x) + (2/((1/3)x)) + (2/((2/3)x)) = 1

- Simplified: (2/x) + (6/x) + (3/x) = 1

- This gives: 11/x = 1/2 --> x = 22

Option 2: 12 Days is NOT correct.

Hopefully, this helped: ?? Answer: A alone can complete the work in 22 days.