An unqualified independent service auditor's opinion in a SOC 1, Type 2 report states that: 

a. Management's description of the system that was designed and implemented through the period in question is presented fairly. 

b. The controls related to the control objectives stated in the description were suitably designed to provide reasonable assurance that the control objectives would be achieved if the controls operated effectively throughout the period. 

c. The controls operated effectively to provide reasonable assurance that the control objectives stated in the description were achieved throughout the period. 

d. All of the answer choices are correct.