By selling 1 dozen ball pens, a shopkeeper earned the profit equal to the selling price of 4 ball pens. His profit percent is

• A. 50%
• B. 40%
• C. <table><tr><td rowspan="2">33</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">%</td></tr><td align="center">3</td></table>
• D. <table><tr><td rowspan="2">31</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td><td rowspan="2">%</td></tr><td align="center">4</td></table>