Final answer:
Isaac's forgetfulness to fill up his car with gas led to the effect of rescheduling an appointment and requiring his wife's assistance.
Step-by-step explanation:
The correct cause-and-effect relationship in the passage provided is that Isaac forgot to fill up his car with gas, which is the cause, and as a result, the effect is that he had to reschedule his appointment. Additionally, because the car was stalled on a busy road, Isaac's wife had to leave work early to take him to a gas station. This scenario highlights the consequences of not maintaining a vehicle's fuel levels, which directly impacts schedules and the need for assistance from others.