Answer:variable interval
Explanation:
In operant conditioning, a variable-interval schedule is defined as that schedule in which a response is received after unpredicted time , because reinforcement has been administered in diffrent non fixed times. The response is slow and steady. Variable means non fixed time which means reinforcement can occur at any time , using various different time zone. Interval refers to time hence this means reinforcement is administered at various times.
Answer: They used irrigation to bring water to crops and fields.
