The correct answer is D. Abundant in supply
Step-by-step explanation:
In the excerpt presented that describes the conditions of slaves during the trip from Africa to America, the word "copious" is used to describe the perspirations (sweat) and the way these made the air "unfit for respiration". This detail and the previous detail "was so crowded that each had scarcely room to turn himself" suggest the word "copious" refer to numerous, plentiful or abundant as everyone in the ship sweat excessively due to the lack of space and therefore the air became highly contaminated. Thus, the word copious in the text means "abundant in supply".