Which one of the following oxides of chromium is amphoteric in nature ?

Amphoteric oxide is an oxide that can neutralize both acid and base. Among the given options chromium(III) oxide( 2 3 Cr O ) is an amphoteric oxide. In acid this oxide forms 3+ 2 6 Cr H O [ ( ) ] and in base chromium (III) oxide ( 2 3 Cr O ) forms 3- 6 Cr OH [ ] . With increasing the oxidation number of the chromium acidity increases and vice versa. So, among the options chromium(III) oxide has an oxidation state is +3 which is in middle. So 2 3 Cr O is an amphoteric oxide. 94. The colour of zinc sulphide is (a) white (b) black (c) brown