Which method is valid for proving that two circles are similar?


a- Calculate the ratio of the diameter to the radius for each circle and show that they are equal.

b- Calculate the ratio of degrees to the circumference for each circle and show that they are equal.

c- Calculate the ratio of the área to the circumference for each circle and show that they are equal.

d- Calculate the ratio of the diameter to the circumference for each and show that they are equal.