Turnover of Water in Temperate Lakes During the Spring and Fall

Multiple Choice

Turnover of water in temperate lakes during the spring and fall is made possible by which of the following?

A) warm, less dense water layered at the top
B) cold, more dense water layered at the bottom
C) a distinct thermocline between less dense warm water and cold, dense water
D) the changes in the density of water as seasonal temperatures change
E) currents generated by nektonic animals