**Concept:** **The question tests on basics of of Coordinate Geometry**

**Solution:**

If we take point C as (1, 1), we get a right angled triangle with base length = 5 - 1 = 4

and height = 4 - 1 = 3

By the Pythagoras theorem

AC = Length of the hypotenuse = √4^2+3^2=16+9

=√25

=5

Alternately, you can use the distance formula between 2 points

= √(y1−y2)^2+(x1−x2)^2

=√4−1)^2+(1−5)^2

=3^2+4^2

√9+16

=√25=5

Option B