21. How would you rank the following in decreasing order of reactivity toward nucleophilic aromaticsubstitution? (most reactive on left)
(A) 4 ＞ 1 ＞ 3 ＞ 2
(B) 2 ＞ 3 ＞ 1 ＞ 4
(C) 3 ＞ 2 ＞ 4 ＞ 1
(D) 1 ＞ 3 ＞ 2 ＞ 4
(E) impossible to predict