15. Arrange the following metals in order of increasing strength as reducing agents: Li, Na, K,Mg.
(A)Na ＞ K ＞ Li ＞ Mg
(B)K ＞ Mg ＞ Na ＞ Li
(C)Li ＞ K ＞ Na ＞ Mg
(D)Li ＞ Na ＞ K ＞ Mg
(E)Mg ＞ K ＞ Na ＞ Li