Final answer:
The most precise data set among the given options is temperature readings with a range of 2°C, as it has the smallest range which indicates higher precision.
Step-by-step explanation:
When looking at various sets of data to yield the most precise measurements in the study of ocean water, one must consider the range of values provided for each data type. Precision refers to how closely multiple measurements are to each other. For the options:
- Temperature readings with a range of 2°C
- Depth readings with a range of 4 km
- Salinity readings with a range of 20%
- Density readings with a range of 40 kg/L
The most precise data would come from the temperature readings that have a range of 2°C. This range is significantly smaller than the ranges presented for depth, salinity, and density, indicating a higher precision. Therefore, a better prediction of oceanic changes can be made from these accurate temperature measurements.