P(0,0) and Q(2a , 0)
Midpoint PQ
x = (x1 + x2)/2 and y = (y1 = y2)/2
Midpoint:
x = (2a +0)/2
= 2a / 2
= a
y = (0+ 0)/2
= 0/ 2
= 0
So midpoint PQ (a , 0)
Answer is the 1st option
(a, 0)