Problem: a and b are two circles . the radius of a is 5 times as large as the radius of b . what is the ratio between the areas of the circles ? 
Options: ['a ) 1 : 8 .', 'b ) 1 : 2 .', 'c ) 1 : 4 .', 'd ) 1 : 25 .', 'e ) 1 : 6 .']
d