TOEFL Listening: TPO-TOEFL听力TPO - 21O268A_W7G1O6EQR$

What is a key feature of a sustainable water system? A. It is able to satisfy short-term and long-term needs. B. It is not affected by changing environmental conditions. C. It usually originates in lakes, springs, or streams. D. It is not used to supply human needs.