In the 1850s, the term “bleeding kansas” referred to
fierce attacks by american indians.
battles during the mexican-american war.
violence related to the slavery issue.
preston brooks’s attack on charles sumner.

the answer is the fierce attacks by American Indians battles during the American war violence related to slavery issue.

In the 1850s, the term "Bleeding Kansas" referred to violence related to the slavery issue.

Explanation:

Bleeding Kansas was a series of violent political confrontations involving anti and pro-slavery groups that took place in the Kansas Territory and in neighboring Missouri, between 1854 and 1861. The motive for the conflict was the question of whether Kansas would enter the Union as a free or slave state. As such, Bleeding Kansas was a proxy war between northerners and southerners about slavery in the United States. The term Bleeding Kansas was coined by Horace Greeley of the New York Tribune; these events were a prelude of the Civil War.

The United States Congress had fought a long battle to balance the interests of pro and anti-slavery forces. The events later known as Bleeding Kansas were a response to the passage of the Kansas-Nebraska Act of 1854, which overturned the Missouri Compromise and sought to implement the concept of popular sovereignty. The inhabitants of each new state should decide whether it would be a free or slave state, however, this resulted in the mass immigration to Kansas of activists on both sides. At one point, Kansas territory had two separate governments, each with its own constitution, though only one was recognized by the federal government. On January 29, 1861, Kansas was admitted to the Union as a free state less than three months before the Battle of Fort Sumter, which started the Civil War in the United States.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.