What is the grand drape in a proscenium theatre?

Question

a
The large curtain located just behind the proscenium arch, raised or lowered to reveal or conceal the stage before and after performances or during scene changes.
b
The large arch or rectangular opening between the stage and the audience seating area.
c
The area between the stage and the first row of the audience seating.
d
The extended portion of the stage that projects towards the audience.

Answer 1

a) The large curtain located just behind the proscenium arch, raised or lowered to reveal or conceal the stage before and after performances or during scene changes.