20.The Barbizon School was a group of artists who _______ natural landscape and themes of country life as vital subjects for French artists in the 1831’s and the 1840’s. Camille Corot and Jean-François Millet were the world-famous artists of this group, which _______ an art movement that eventually led to Impressionism.
(A) built up; promised
(B) established; constituted
(C) formed; developed
(D) constructed; encouraged