question_answer

A circle is drawn to pass through the extremities of the latus rectum of the parabola\[{{y}^{2}}\text{ }=\text{ }8x\]. It is given that this circle also touches the directrix of the parabola. Radius of this circle is equal to

A)  4                    

B)  \[\sqrt{21}\]

C)  3                    

D)  \[\sqrt{26}\]