Final answer:
The weakness in the internal control of a computer system is when machine operators distribute error messages to the control group and do not have access to the complete systems manual.
Step-by-step explanation:
The weakness in the internal control of a computer system is option B) Machine operators distribute error messages to the control group. This constitutes a weakness because error messages should be handled by the appropriate individuals responsible for fixing the errors, not distributed to a wider audience. This can lead to confusion, delays in resolving issues, and potential security breaches.
Option C) Machine operators do not have access to the complete systems manual is also a weakness in internal control because operators may not have the necessary guidance or information to properly operate and troubleshoot the system. This can result in errors or inefficiencies.
Option D) Machine operators are supervised by the programmer is not a weakness in internal control. In fact, it is an important control measure to have supervision and oversight by a programmer to ensure proper functioning of the system and adherence to protocols.
Therefore, the correct answer is B) Machine operators distribute error messages to the control group and C) Machine operators do not have access to the complete systems manual.