The election of 1800 demonstrated that

the Alien and Sedition Acts were constitutional.

the electoral college worked smoothly.

the US government was stable.

presidential campaigns did not need personal attacks.

Let's look at the answers:

the Alien and Sedition Acts were constitutional.

-the elections have nothing to do with constitutionality of laws, so we reject this answer

the electoral college worked smoothly.

-this is also false! in fact, the problems with the electoral college in this election were a reason for the 12th Amendment later

the US government was stable. - we choose this answer, because we have good reasons to reject every other answer!

presidential campaigns did not need personal attacks.

-this is false! This election was distinguished by many personal attacks