an auditor is required to test the design and operating effectiveness of a client$$s internal control under which of the following circumstances?

a$)$ The auditor plans to decrease the assessed control risk and therfore allow for a higher detection risk

b$)$ When the auditor is attempting to test multiple finacial statements assertions with a single test of details

c$)$ the auditor has assessed the inherent risk as low and plans to offset the risk with an increased number$/$quantity of tests of details