Prior to the Civil War, how was the issue of slavery related to westward expansion? A)The large number of plantation-style farms in western territories made it likely that slavery would expand westward
B) The possible addition of new states created from western lands raised concerns over the balance between free and slave states.
C) The westward expansion into lands formerly controlled by Spain helped create a Hispanic labor market to replace the use of slave labor.
D) The discovery of gold western territories led to a large increase in the use of slave labor in gold mines.

answer:   migrations were important in the neolithic period. "two major migrations passing through southeastern europe were confirmed by the means of archaeo-genetic studies."

the first migration was the early neolithic period -- 6,000 before common era (bce) -- when the first farmers, from anatolia -- asia minor -- spread through europe. the second migration occurred during the early bronze age (3,000-2,500 bce) when the so-called "steppe population," from the eurasian steppe, replaced much of northern europe's previous population.

the first farmers of northern and western europe passed through southeastern europe with limited hunter-gatherer genetic admixture, which occurs when two or more previously isolated populations begin interbreeding. however, some groups that remained mixed extensively -- without the male-biased, hunter-gatherer admixture that prevailed later in the north and west, according to latest discoveries. southeastern europe continued to be a nexus between east and west, with intermittent genetic contact with the steppe people up to 2,000 years before the migrations that replaced much of northern europe's population.

"in some places, hunter-gatherers and incoming farmers seem to have mixed very quickly," says iain mathieson, a geneticist at the university of pennsylvania, who was first author of the paper. "but, mostly, the two groups remained isolated, at least for the first few hundred years. these hunter-gatherers had been living there for thousands of years, and it must have been quite a shock to have these new people show up -- with a completely different lifestyle and appearance."

once he became head of state in 1915, venustiano (his name was not victoriano) carranza was able to implement some of his ideas, such as the drafting and the promulgation of the mexican constitution of 1917, which is still the current constitution of that country.