A section of code that may only be executed by one process at any one time is

CPM
Critical resource
Critical region

The correct answer is C. Critical region.

A critical region is a section of code that may only be executed by one process at any one time. This is to ensure that the data in the critical region is not corrupted.

A critical resource is a resource that is shared by multiple processes. This resource must be managed carefully to ensure that it is not accessed by multiple processes at the same time.

CPM is a project management technique. It stands for Critical Path Method.

Gray code

is a type of code that is used to represent numbers. It is a non-repeating code.

None of the above is a section of code that may only be executed by one process at any one time.