Why did so many reform movements gain strength between 1830 and 1860

Second Great Awakening

Explanation:

US 1830 to 1860 was a crucial time for american reform, i.e improvement for betterment. As the period involved many reform movements : Abolitionist movement (for removing slavery), temperance movement (to reduce alcohol sale), other education & labour reform movements.

The primary reason of these series of reforms has been 'Second Great Awakening'. It occurred as a protestant religious revival in US during 19th century. This spread emotional preachings as a part of religion, which ignited the values of freedom & liberty; in the minds of US population.

c or d both can be the answer