Which policy was a last-ditch effort by the US Congress to preserve the Union and stave off secession

The answer is the Compromise of 1850. This compromise wanted to stop the secession conflicts that were happening in the US. The said law was able to diffuse the on-going conflicts with regards to the lands acquired from the Mexican-American War. It was able to stop some issues of the ongoing crisis but citizens have different opinions with regards of this law

Explanation:

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since most of current immigration into the u.s., both legal and illegal, is coming from latin america. it would be very difficult to imagine or rationalize a country my fellow citizens are trying desperately to flee into, would pose a threat to my prosperity or freedom. since the u.s. has a long history of intervention, but no record of permanent occupation, i would not feel oppression is the main objective.  

the largest free trade nation, along with the largest gdp in the world wanting to expand it's economic policy on us, and including us, could only be positive. the u.s. government has no interest in, or way of simply forcing american culture on us. and has no track record of it. other nations that adopted american social culture, or "americanization" did so voluntarily, mainly through the choice of allowing american businesses and u.s. citizens to come into their nations, as free operatives.

the correct answer is ''the programs costs have risen dramatically in the recent past'' hope this !