How did many twentieth-century artists respond to the extravagant furniture designs popular in the sixteenth-nineteenth centuries?
a. by designing country-inspired pieces
b. by designing extravagant, detailed pieces
c. by designing asymmetrical, detailed pieces
d. by designing simple, clean pieces

Simple and clean. "Form follows function" was a guiding principle. Look up the Bauhaus, le courboisier, and more van der rohe. Also things like ames chairs and industrial design, and look up Scandinavian art and design too. While these did give us some awesome style and landmark designs, it also unfortunately gave us IKEA.