The correct option is B 3 : 5
Consider the fraction 1220. Note that the HCF of 12 and 20 is 4. If we now divide both the numerator and the denominator of the given ratio by 4, the value of the ratio still remains the same.
i.e., 1220=12÷420÷4=35
Thus, the ratio 12:20 in its simplest form is 3:5.