A particle is moving in a uniform circular motion with constant speed v along a circle of radius r. The acceleration-of the particle is

• A. zero
• B. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>V</center></td><td rowspan="2"></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">r</td></tr></table>
• C. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>V</center></td><td rowspan="2"></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">r²</td></tr></table>
• D. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>V²</center></td><td rowspan="2"></td><td rowspan="2"></td></tr><tr><td style="text-align: center;">r</td></tr></table>