Which is the correct use of the word “emerged”?
west african kingdoms emerged to form one union.
trade emerged as a main source of income.
gold emerged from one merchant to another.
which merchant will best emerge the wealth?

I believe the answer is: Trade emerged as a main source of income.

The word 'emerge' means something that start to become prominent or dominant as the time goes by.

During its early introduction, trade was not really popular since many people still choose to take care of their own agricultural field as their main source income. It took hundred of years before trade finally acknowledge as something profitable

other sources of text

explanation:

this can be magazines, news reports, scholarly articles, textbooks, research papers etc.

trade

explanation: