Question: Estuaries are dynamic ecosystems where salt water and fresh water mix. Usually this happens as fresh water flows from a river to an ocean. When would you expect the concentration of salt in the estuary water to be LOWEST near the mouth of the river?

  Options: 
 A. when the river flow is low and the tide is low
 B. when the river flow is high and the tide is low
 C. when the river flow is low and the tide is high
 D. when the river flow is high and the tide is high 
Answer: B