The circles B and D are similar since the radius of the former is as twice as the radius of the latter.
<h3>Are the two circles shown in the figure similar?</h3>
By geometry we know that circles are defined by only one characteristic: radius. If two circles are similar, then the radii must be <em>different</em>. After a quick look at the figure, we conclude that the radii are and . Hence, the circles B and D are similar since the radius of the former is as twice as the radius of the latter.