What impact did European contact have on Native American population between 1500 and 1620? A) population increased B) population decreased C) population remained stagnant D) population showed no changes

It decreased and very significantly so!

Most of native Americas died of diseases brought by Europeans; but some were also killed directly by the Europeans. Many also mixed with the Europeans (by marriage or rape ...) so there was also a mixed indigenous-white population.

ps. C and D is essentially the same answer