The ratio 1:2 can be written in fraction form as
[tex]\frac{1}{2}[/tex]we can multiply the numerator and denominator by the same number and the result will be the same, for instance,
[tex]\frac{1}{2}=\frac{1}{2}\times\frac{2}{2}=\frac{2}{4}[/tex]then, 1/2 is equal to 2/4.
However, 3/5 and 4/6 are not equal to 1/2 because there is no a number which gives us 3/5 and 4/6 from 1/2. Then, the answer is option A
