Which of the following best summarizes why the missouri compromise needed to be replaced by the compromise of 1850?
members of congress wanted to end the question of slavery in the u. s.
the u. s. wanted to sell the territory gained after the mexican-american war to build railroads, and the missouri compromise prevented it.
congress decided that the people should be able to decide whether the territory gained in the mexican-american war should be allowed to have slavery.
the territory gained after the mexican-american war was mainly below the missouri border, and u. s. leaders believed slavery would be necessary to ensure settlement.

The Missouri Compromise needed to be replaced by the Compromise of 1850 because members of Congress wanted to end the question of slavery in the United States.

The Compromise of 1850 is a set of five bills passed by the Congress of the United States in September 1850, which appeased a political confrontation between slave states and free states. This crisis, which lasted five years, had its origin in the disagreement on the status that territories acquired after the US intervention in Mexico (1846-1848) should receive and reached its maximum degree of tension with the problem of fugitive slaves.

In short, of the three new territories annexed by the United States, California became a free state while Utah and New Mexico became slave territories. The commitment was welcomed with relief, although on each side some specific clauses were disliked.

i think it was   tsar alexander ii