19. An air filled parallel plate capacitor has a capacitance of 1μF. The plate separation is then doubled and a wax dielectric is inserted, completely filling the space between the plates. As a result, the capacitance becomes 2μF. The dielectric constant of the wax is ______. (A) 0.25 (B) 0.5 (C) 2.0 (D) 4.0 (E) 8.0