Answer:
a. Missouri Compromise.
Step-by-step explanation:
The US government passed an agreement called the Missouri Compromise in 1820 that allowed Missouri to be a slave state. This agreement made a sectional demarcation by allowing the state of Missouri to be a slave state while making Maine a free state and also the areas north of Missouri to be also free soil.
As the issue of slavery was a burning issue for the Union, this compromise led to a backlash from the people. So, the people expressed their criticism of the 'representatives' or members of the Congress who helped in passing the controversial agreement.
Thus, the correct answer is option a.