How did plastic revolutionize the art of furniture design?
a.) designers could create works that were soft and colorful.
b.) designers could create works that were sturdy and moldable.
c.) designers could create works that were patterned and sturdy.
d.) designers could create works that were firm and colorful.

B. Designers could create works that were sturdy and moldable. 

I do hope this isn't from a test, if it is you should be doing your own work, but the general idea is that plastic made it easier to make decently sturdy and extremely moldable, malleable, objects. That just made collages, sculptures, and other physical artworks all that much easier to create.

What it's saying is that colored pieces of canvases is a piece of art