Why was the three-fifths compromise necessary? (select all that apply.) a. southerners were concerned that northerners would establish plantations and drive down the price of the south’s cash crops. b. northerners feared that southerners would free their slaves, causing a mass migration of former slaves to northern states. c. northerners believed that if slaves were counted as part of the population, then the southern states would dominate the house of representatives. d. southerners feared that they would be taxed twice if each slave were counted as property as well as part of the population.