What is constant bit rate (CBR) in MPEG-2?

What is constant bit rate (CBR) in MPEG-2?

a) An operation where the bit rate is constant from start to finish of the compressed bit stream.

b) A variety of MPEG video compression where the amount of compression does not change.

c) Traffic that requires guaranteed levels of service and throughput in delay-sensitive applications such as audio and video that are digitized and represented by a continuous bit stream.