Which physical characteristics divide the oceans into zones?

• A. Sunlight, temperature, salinity, and density
• B. Wave height, current speed, turbidity, and pH
• C. Depth, pressure, salinity, and acidity
• D. Temperature, pressure, color, and viscosity

Answer: (A)

The main idea is that the ocean is divided into vertical zones by light and by how water density changes with depth. Sunlight sets the photic zone where photosynthesis can occur; below that, in the aphotic zone, little or no light penetrates. Temperature and salinity determine how dense the water is, and this density structure creates layered water masses: a lighter surface layer above denser deeper waters, with a thermocline where temperature shifts rapidly and a pycnocline where density increases with depth. Because light availability and density stratification together define distinct vertical regions, the combination of sunlight, temperature, salinity, and density best describes how oceans are zoned. Other options focus on surface conditions or properties that don’t consistently establish the broad depth-based divisions used to describe ocean structure.