$\"\"$

Connect the points $\"\"$ and $\"\"$ then it forms a right angle trianle $\"\"$ .

Observe the figure:

If $\"\"$ then $\"\"$ .

If $\"\"$ then $\"\"$ ,therefore $\"\"$ .

From Pythagarous rule:

$\"\"$ .

Substitute $\"\"$ and $\"\"$ .

$\"\"$

Hence the answer is $\"\"$ .

$\"\"$

The correct option is $\"\"$ .