题目

In the beauty competition, women are asked_______ some of the exercises ________ the music.   A. performing to; to                                B. performing; with   C. to perform; to                                    D. to perform; by 答案：C 0.5 L　1 mol/L的FeCl3溶液与0.2 L　1 mol/L的KCl溶液中，Cl－浓度比为 [　　] A． 15∶2 B． 1∶1 C． 3∶1 D． 1∶3