(asking again because point-hogs exist)
Assume n represents the number of inputs. The possible number of states within a truth table can be calculated using which of the following formulas?
2n
2/n
n/2
2 * n
The answer is 2-to-the-power-of-n, since for every input, the number of different combinations doubles. From your list I think answer A is meant to indicate 2ⁿ.