What event completes this timeline?

A. The Constitutional Convention is held in Philadelphia.

B. George Washington is elected president.

C. Three states vote for ratification with little debate.

D. The Constitution goes into effect.

The answer is D. here but for some others, it will be Enough states ratify the constitution for it to go into effect. which may also still be the answer D. (apex)

D. The Constitution goes into effect

When the Constitutional Convention met for the first time with a quorum at the Pennsylvania State House in Philadelphia to revise the Articles of Confederation on May 25, 1787 the drafting of the Constitution began and was ended on the 17th day of September 1787. Then the ratification process for the Constitution were followed and began that day and ended when the final state, Rhode Island, ratified it on May 29, 1790. The time span covered until it goes into effect is 5 years and 9 months from March 25, 1785 to January 10, 1791.