The best way to justify which answers are correct are to calculate the circumference and the area for each of the circles with the given radii. I organized this information into a chart.
Circumference | Area
1/2 3.14 0.785
1 6.28 3.14
1 1/2 9.42 7.065
2 12.56 12.56
2 1/2 15.7 19.625
The first three choices will result in a numerical value for the radius that is smaller than the area.