Question

the fugitive slave act upset many northerners because
they wanted it to be stricter.
it required them to allow slavery in free states.
it forced them to support the recapture of escaped enslaved persons.

Explanation:

The Fugitive Slave Act was upsetting to Northerners because it forced them to support the recapture of escaped enslaved persons. Northerners, many of whom were against slavery, were compelled by this act to assist in returning escaped slaves to their owners, which went against their anti - slavery sentiments. The option "they wanted it to be stricter" is incorrect as Northerners generally opposed the act, not wanted it stricter. The option "it required them to allow slavery in free states" is also incorrect as the act was about returning escaped slaves, not about allowing slavery in free states.

Answer:

C. it forced them to support the recapture of escaped enslaved persons (assuming the third option is labeled C, if the original options had labels like A, B, C with A being "they wanted it to be stricter", B being "it required them to allow slavery in free states", C being "it forced them to support the recapture of escaped enslaved persons")