Please help. How was the Northern approach to slavery different before the 1850s?

A
Northerners openly supported slavery while they objected to slavery by the 1850s.
B
Northerners spoke rarely about slavery while it became the main topic of debate in the 1850s.
C
Northerners believed in economic growth, so they continued to profit off of slave labor in the 1850s.
D
Northerners objected to slavery due to moral reasons, but they protested the expansion of slavery for political reasons in the 1850s.