The distance between the point in my center and any point on my outline is equal. What am I?

Question

a.Triangle
b.Octagon
c.Circle
d.Square

Answer 1

http://www.google.com/imgres?imgurl=https://www.msu.edu/user/socomm/bullseye.gif&imgrefurl=https://www.msu.edu/user/socomm/Granger.html&usg=__tTk_gfxyL-vZR0gU4PPQKeLoXmE=&h=384&w=384&sz=7&hl=en&start=0&zoom=1&tbnid=C8rOiLnu4oqfJM:&tbnh=116&tbnw=116&ei=T3gwTZzRH4OB8gaVu-ncCA&prev=/images%3Fq%3Dbullseye%26um%3D1%26hl%3Den%26biw%3D994%26bih%3D636%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=122&vpy=315&dur=651&hovh=179&hovw=179&tx=115&ty=123&oei=T3gwTZzRH4OB8gaVu-ncCA&esq=1&page=1&ndsp=18&ved=1t:429,r:6,s:0