Which best describes an opportunity cost

Plz me asap. upon arrival of european powers on american soil, a quick end came to many native populations. numbers were devastated the longer europeans were present. many empires such as the aztec and inca were taken by force. the natives’ weapons of arrows and rocks were no match for gunpowder, steel swords, and horses. yet even after hostile takeovers, the native americans continued to suffer in numerous ways. according to las casas, the harshness of the encomienda system took many native lives. examples of such harshness included beatings by colonists and exhaustion caused by never-ending labor. natives were forced into slave labor in order to process colonists’ crops such as sugar cane and tobacco. these crops were referred to as “cash crops”. cash crops are crops grown not for sustenance but because they are extremely profitable. the colonies would have natives tend to these crops and they would then be exported to other european nations for high prices in order to make manufactured or processed goods. native slaves were worked for long hours in extremely hot temperatures with very little food, water, or breaks. they suffered savage beatings for working too slow and some were killed for refusal to work due to their exhaustion. poor health is another struggle natives faced upon european colonization. many natives died from hunger once colonists started to take their land. colonists’ cattle trampled native crops such as corn and squash. but possibly the most devastating factor in declining native populations were the diseases brought by europeans and against which the native people had no immunity. these included smallpox, typhus, chicken pox, mumps, and measles. hundreds upon thousands of natives fell to such diseases. entire villages were wiped out in mere days of the first symptom. native cities throughout the americas became desolate from the fast spread of disease. native american empires such as the aztec and the inca fell to the spanish and portuguese in the 1500s. the aztec alone had between sixteen and eighteen million people under their rule before europeans landed on the continent. why were these empires unable to fight the inevitable take over of european powers? use evidence from the text to support your answer.