Why are Chinese paintings seldom framed?

A、Because Chinese people do not find frames aesthetically beautiful.;

B、Because wood was expensive in China, and only rich people could afford buying expensive wooden frames.;

C、Because in China paintings usually are rolled into scrolls, and one can't roll a painting into a scroll if it is inside a hard frame.;

D、Because a painting frame had some religious meaning and only the emperor had a right to use them.