Final answer:
The incorrect reason for the increase in slave trade was that 'Missionaries enslaved Africans to convert them to Christianity'. The increase was primarily due to economic reasons such as the need for labor on cash crop plantations, the exchange of slaves for goods, and the use of slavery as punishment.
Step-by-step explanation:
The reason that was NOT a reason for the increase in slave trade during the period in question is: d) Missionaries enslaved Africans to convert them to Christianity. While conversion to Christianity was used as a justification for enslavement, it was not a motive for the increase in slave trade; the major reasons were economic. A large labor force was needed in the Americas to grow cash crops such as sugar and tobacco, which provided profits for European markets. Additionally, African kings did expand their kingdoms by trading slaves for manufactured goods. Slavery as a punishment for criminals or debtors also contributed to the increase, but missionaries did not enslave Africans for the purpose of conversion.
Instead, the demand for labor in cash crop production and the benefits of slave trade to African rulers were significant factors. The religious argument of exposing Africans to Christianity was ironic because very little conversion occurred due to the emphasis on productivity and profits