Which of the Following Statements Regarding Turnover Is True

Which of the following statements regarding turnover is true?

A) In fall turnover,dense water at 4°C sinks and disturbs sediments in the benthic zone.
B) In fall turnover,dense water at 4°C rises and disturbs sediments in the benthic zone.
C) The surface water gets to 4°C only by cooling.
D) Fall turnovers and spring turnovers are exactly the same.