The correct option is A 12
Given : y=2x+14 is tangent to
y2=4ax
here, slope of tangent =2
Consider y2=4ax
if slope of tangent is m then point on parabola will be(am2,2am)
So point on parabola is (a4,a)
This point will satisfy the equation of tangent , hence
⇒a=2(a4)+14
⇒a=12
Hence, Option A is correct answer