Which of the following led to the most sectional strife over slavery in the first half of the 19th century?

The westward expansion had caused a major sectional strife among the US due to the following reasons. 1. President Polk, who was the president of the United States at that time, was not supportive of the treaties made by the North. At the time, sectional crisis had been one of the major problems in the United States.

2. The stand of Texas in terms of slavery.  The annexation of Texas had caused one of the reasons of the sectional strife. Texas was known for being a pro-slavery state before its annexation to the US. Because of this many Whigs have fought against Democrats in Congress because of the possibility of the expansion of slavery in the westward expansion

c. free trade can lead to low pay for workers in poorer countries.

incident infrared radiation is blocked. visible and ultraviolet radiation heat   earth.

earth radiates infrared radiation. infrared radiation is blocked and heats earth. visible and shortwave radiation heat earth.

earth radiates longwave radiation

longwave radiation is reflected downward longwave radiation heats earth