Which of these happened for the first time during the Ghana empire? A. Europeans begin to purchase people into slavery
B. people begin to trade with other people
C. Gold was discovered to be a valuable good
D. A West African kingdom was led by Muslim rulers

30 and 44 are b

explanation:

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: