Final answer:
The correct inequality for the scenario where each of 5 buses carries fewer than 20 students on a field trip is s/5 < 20, showing that the total number of students divided by the number of buses must be less than 20. Therefore, the correct option is d. s/5 < 20.
Step-by-step explanation:
The inequality that represents the situation where there are 5 buses and each bus is to have fewer than 20 students on a field trip would be d. s/5 < 20. This inequality states that when the total number of students (s) is divided by the number of buses (5), it should be less than 20 to meet the requirement of having fewer than 20 students on each bus.