To solve this question we will use a theorem called the intersecting secant theorem which states that "if 2 secants of a circle intersect outside the circle then product of their segments are equal".
Thus, applying this theorem in this question we see that:
![AC* BC=EC* DC](https://img.qammunity.org/2019/formulas/mathematics/middle-school/o0g9p5bi767nktgm7we20xwaxrf9jja3y8.png)
Thus,
![10* 6=12* DC](https://img.qammunity.org/2019/formulas/mathematics/middle-school/xx9g35ebbqbtc8w1bqkp1aog9k7t7l4m24.png)
Thus,
![DC(10* 6)/(12)=5 cm](https://img.qammunity.org/2019/formulas/mathematics/middle-school/z9ug8p0ns94g4rpt650azevs00t66hkaoy.png)
Thus, out of the given options, the first option is the correct option.