Final answer:
A violation of the segregation of duties in an internal control structure is when one person is responsible for both signing and distributing payroll checks, as it concentrates control and increases the risk of fraud.
Step-by-step explanation:
One characteristic of an effective internal control structure is the proper segregation of duties. This means that tasks should be divided among individuals to decrease risk of error or fraud. For example, the person responsible for signing checks should not also be responsible for recording payroll expenses, as combining these tasks can create a conflict of interest and a lack of checks and balances.
The option that is a violation of segregation of duties is: a. signing and distributing payroll checks. This is because when one person is tasked with both signing and distributing checks, there could be a risk of fraud, as this individual has control over the issuance of checks without oversight.
Other options, such as the approval of time cards by a production supervisor, do not inherently imply a lack of segregation of duties, and hiring employees and authorizing changes in pay rates would typically involve different departments or layers of authorization.