What should be a possible reason for the demise of Mayan civilization??? Please answer ASAP thank you

Which of the four varnas are soldiers placed in? a. sudra b. brahmin c. vaishya d. kshatriya

"“forty or fifty years ago, many people thought that simply transferring technologies from industrialized to developing countries would close the technology gap. now we know that technologies developed in industrialized countries may not be suitable for use in other environments. they may require a particular type of infrastructure to operate. they may need specialized parts or knowledge to mend when they break we now understand that innovative capacity must be built in different ways." - united nations secretary-general ban ki-moon based on the secretary general's comments, which of these would be most important for a country to improve? a) native literature b) transportation grid c) cultural traditions d) construction styles

At these trading houses we have kept prices low. we have driven out private traders and those who would make the indians suspicious and fearful of us. in doing so, we have earned the good will of the indians. a letter enclosed shows the effect of this. the indians see the advantage of purchasing from us and request that we establish trading houses among them. in one area this is particularly interesting. the congress must know how much we want to control a large stretch of land on the mississippi river. this would allow us to present as strong of a defense on that side of our territory as on our eastern border. we already control what is below the yazoo river. however, the country between the yazoo river and the ohio river belongs to the chickasaw indians. this tribe refuses to sell its land, but they have recently shown a desire to begin farming. this leads to buying goods and comforts. if we grant these desires, we may be able to secure land on the mississippi. now that trade is expanding among the indian tribes, congress may wish to point our citizens in another direction. the missouri river is not well known to us. it crosses a mild climate and offers a route from the western ocean to the atlantic. an intelligent officer and a team of men might explore the whole route of the river to the western ocean. they could speak with natives, find opportunities for our traders, and return with information after two summers. their arms, tools and gifts for the indians would be the primary costs of the expedition. it would benefit our nation to explore this territory because it offers the only easy way to travel across the continent. the interests of trade give congress the power to approve this expedition. learning more about the geography of our continent is another reason to make this voyage. $2,500 is requested for the purpose of extending trade across the united states. this sum will cover the entire undertaking. what did thomas jefferson suggest congress do in response to the native americans?