Which of the following best describes a situation where a bidirectional shift register would be preferred over a unidirectional shift register in a digital system?

Correct option is B

A bidirectional shift register can shift data:

Left, and
Right

This capability makes it ideal for applications such as:

Rotating data (circular shifting)

Arithmetic operations needing multi-directional shifts

Serial communication systems requiring forward/backward shifting

A unidirectional register cannot perform these operations because it shifts only in one direction.