The house in a proscenium theatre refers to:

a
The extended portion of the stage that projects towards the audience.
b
The offstage areas on either side of the stage, concealed from the audience's view.
c
The seating area for the audience in the theatre, including the rows of seats facing the stage.
d
The area of the stage closest to the audience.

c

The seating area for the audience in the theatre, including the rows of seats facing the stage.