It sounded good to my ears
The science that isn't considered a social scence from the ones you've mentioned would definitely be biology as it studies the relation between things on a very small level and often includes dead specimens.
The Europeans in the Caribbean felt the need to bring in enslaved Africans as laborers because the native American Indian workers had become physically weak due to diseases and the Caribbean plantations were in requirement of stronger labor force. The Africans by birth were very strong and they as slaves would perfectly suit the needs of the Caribbean plantations.
The three factors that are found in the system of checks and balances are; The president can veto legislation passed by congress, Congress has the power to impeach the president for misconduct, and the Supreme Court may declare laws unconstitutional.