Question

Please do not answer unless you are correct..I will award double points

Answer 1

The dot product of two orthogonal vectors is always zero. 

Vector u can be expressed (-5,-3) as its ends on this points and starts from origin. The dot product of vector u with vector given in option A results in zero.

(-5, -3) · (1/5, -1/3)

= -5(1/5) + (-3)(-1/3)

= - 1 + 1

= 0 

Hence first option is the correct answer