Aquatic biomes cover approximately three-quarters of Earth's surface. Examples of aquatic biomes include lakes, streams and rivers, wetlands, estuaries, and oceans. Different types of aquatic biomes are distinguished by their physical and chemical characteristics, their depth, and, for some biomes, their distance from shore. Many temperate lakes undergo semiannual turnover, a process that mixes the surface and bottom waters, resulting in the redistribution of oxygen and nutrients.
Aquatic biomes can be distinguished by chemical characteristics such as dissolved oxygen content and salinity and by physical characteristics such as water flow.
Which five of the following statements about aquatic biomes are true?

a. The lowest levels of dissolved oxygen in a stream are generally found in its turbulent headwaters.
b. Wetlands have slow water movement or no water movement and no turnover.
c. Tropical coral reefs generally exist in relatively shallow areas of the ocean.
d. Estuaries are very productive and are used as breeding grounds by many species of fish.
e. A freshwater organism permanently attached to the substrate would be unlikely to survive and reproduce in an estuary.
f. Temperature drives water movement in some lakes.
g. All wetlands have soils that dry out periodically.