[Q]: How does the sentence end?

At the art museum there were many genres of art, including colorful pop pieces to classic art. My favorite was the 

[A]: classic art because it was old.


[Q]: How does the sentence end?

Nelson bought a dehumidifier and Joseph did not, so 

[A]: Joseph had more water in the air in their house.


[Q]: How does the sentence end?

Elena wanted to have a serious conversation with Laura who did not, so 

[A]:
Elena adopted a grave tone.