Management has taken immediate action to address an observation received during an audit of the organization's manufacturing process.Which of the following is true regarding the validity of the observation closure?

a. Valid closure requires evidence that ensures the corrected process will function as expected in the future

b. Valid closure requires the client to address not only the condition, but also the cause of the condition

c. Valid closure of an observation ensures it will be included in the final engagement report

d. Valid closure requires assurance from management that the original problem will not recur in the future