Witch is not one of the three main periods history has been divied in to?

The name for the compound with the formula cr2o3 would be written as a. chromium(i) oxide. c. chromium oxygen. b. chromium(ii) oxide. d. chromium(iii) oxide.

Excerpt from w. e. b. du bois jon reese 4 du bois was one of the first male civil rights leaders to recognize the problems of gender discrimination. he was among the first men to understand the unique problems of black women, and to value their contributions. he supported the women's suffrage movement and strove to integrate this mostly white struggle. he encouraged many black female writers, artists, poets, and novelists, featuring their works in his crisis magazine and sometimes providing personal financial assistance to them. the cause was that w. e.b. du bois encouraged many black female writers, artists, poets, and novelists. what was the result? think about cause-and-effect relationships.

“well,” he says, “there’s excuse for picks and letting-on, in a case like this; if it warn’t so, i wouldn’t approve of it, nor i wouldn’t stand by and see the rules broke—because right is right, and wrong is wrong, and a body ain’t got no business doing wrong when he ain’t ignorant and knows better. it might answer for you to dig jim out with a pick, without any letting-on, because you don’t know no better; but it wouldn’t for me, because i do know better.” the meaning in this excerpt is