N is the foot of the perpendicular from a point P of a circle with radius 7 cm, on a diameter AB of the circle. If the length of the chord PB is 12 cm, the distance of the point N from the point B is

• A. <table><tr><td rowspan="2">6</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>5</center></td><td rowspan="2">cm.</td></tr><tr><td align="center">7</td></tr></table>
• B. <table><tr><td rowspan="2">12</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2</center></td><td rowspan="2">cm.</td></tr><tr><td align="center">7</td></tr></table>
• C. <table><tr><td rowspan="2">3</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>5</center></td><td rowspan="2">cm.</td></tr><tr><td align="center">7</td></tr></table>
• D. <table><tr><td rowspan="2">10</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>2</center></td><td rowspan="2">cm.</td></tr><tr><td align="center">7</td></tr></table>