Answer:
B) error rate
Explanation:
error rate basically refers to how many mistakes that a user makes while performing a task, the severity of these mistakes are and how easy it is to recover from these mistakes. So error rate is recorded when user makes a mistake while performing a task. The description of the error is also provided with the error. Then the severity of these error is recorded and the error are classified. IT is time consuming to record the errors but error rates are useful in providing usability of a task and helps to identify the errors. It also helps to identify the cause of occurrence of an error.
