The equation of the tangents drawn from the origin to the circle x²+y²−2rx−2hy+h²=0 are
a. x = 0, y = 0
b. (h² - r²)x - 2rhy = 0, x = 0
c. y = 0, x =4
d. (h² - r²)x + 2rhy = 0, x = 0