I assume that you are asking about the increase in trade between the Caribbean and Africa that began in the 1500s. If so, there are two possible answers. One answer is to say that slavery caused the increase while the other answer is to say that the creation of colonies in the Caribbean caused the increase. The correct answer depends on your perspective.
The immediate cause of the increase in trade was the beginning of slavery. The main thing that Africa had that people in the Caribbean wanted was slaves. The elites of the Caribbean needed laborers and imported those laborers (as slaves) from Africa. This caused the increase in trade.
But you can also say that it was the creation of colonies that actually caused the increase in trade. You can say this because the creation of colonies led to a need for slavery. When the colonies were set up, their economies were based on agriculture, mainly on sugar. The sugar plantations needed unfree labor. Therefore, Europeans started to ship slaves from Africa to the Caribbean.
Either of these answers is possible. You need to determine which you feel is right. You may want to consult your class notes to see which answer your instructor wants to see.