7. (1) Machines are complete mysteries to me, and this has resulted in some embarrassing service calls at my home. (2) For example, there was the time I called in a repairman because our refrigerator was too warm. (3) Imagine my humiliation when he told me that the cause of the problem was a dirty filter, which I didn’t know existed and therefore hadn’t cleaned even once in the two years we owned the refrigerator. (4) The best example of my brilliance with machines, however, has to be the time I called for someone to fix my washing machine. (5) The repairman’s solution was simply to put the plug back in the outlet, from which it had been jarred loose by the constant vibration of the washer.

The tone of this passage is

a. straightforward.

b. disbelieving.

c. self-mocking.