How many states still allow slaves ?

With an american government question

Which of the following was a key accomplishment of the people of songhai? a. they had a strong military and became the largest empire in west africa. b. they established a center of islamic scholarship. c. they worked with iron and prospered from the gold-salt trade. d. they dominated in the trade of ivory, enslaved people, and animal skins.

Congress checks on the power of the presidency by overriding a presidential reversal or veto. debating the bill in both of the houses. making laws without presidential review. sending the bill back to several committees