we know that
If the scalar product of two vectors is zero, both vectors are orthogonal
A. (-2,5)
(-2,5)*(1,5)-------> -2*1+5*5=23-----------> are not orthogonal
B. (10,-2)
(10,-2)*(1,5)-------> 10*1-2*5=0-----------> are orthogonal
C. (-1,-5)
(-1,-5)*(1,5)-------> -1*1-5*5=-26-----------> are not orthogonal
D. (-5,1)
(-5,1)*(1,5)-------> -5*1+1*5=0-----------> are orthogonal
the answer is
B. (10,-2) and D. (-5,1) are orthogonal to (1,5)