**The correct option is (C) 10.**

**Explanation:**

Focal length of concave mirror = f = 20 cm

magnification = m = 2

m = (–v / u)

∴ 2 = (–v / u)

Hence v = –2u .....(1)

Also (1/f) = (1/v) + (1/u)

∴ (1/f) = (1 / –2u) + (1/u)

(1/f) = {(– 1 + 2) / (2u)} = (1 / 2u)

∴ 20 = 2u

u = 10 cm i.e. position of object is 10 cm.