After Congress has approved a proposed amendment to the Constitution, what then must take place before that amendment becomes law?

The correct option for above statement is:

B. Three-quarters of the states must approve it.

Explanation:

Congress has the authority to recommend amendments. The submitted improvement must receive the support of at least two-thirds of the House and two-thirds of the Senate. Members at a national meeting may propose amendments. At least two-thirds of the state governments must request Congress to call a national convention.

After Congress has approved a proposed amendment to the Constitution, in order for that amendment to become a law, the individual states must "ratify" the amendment, to ensure that the states agree it is a good option.