The element carrying the entire weight of the plot is
a. stage directions
b. characters
c. structure
d. theme

I believe it is the characters that is carrying the entire weight of the plot.
Why?
because it is the character that relays the story's message to the audience or to the readers.
If the character were not able to do well on her acting, then possibilities are the audience were not able to get the message.

∵they depict sad lonely people  ∵  figures in them have long limbs and faces, similiar in style to paintings by el greco.