African slaves were brought to the English colonies to meet the demand for

This is tricky, and here's why. The obvious, superficial answer is cotton, and you might throw tobacco in there, and sugar as well. Those are the answers they would be looking for. The other answer is that the English were carving up Africa under the pretense of ending Arab slavery, so there would be a demand for success in imperial colonial adventures. Other things to look at are the Balfour Agreement, Berlin Conference, Triangle Trade, and Navigation Acts.