Scientists have believed for many years that marine temperatures drop as ocean depth increases. what experimental method would best test this hypothesis, and why?

a. bring samples of ocean water from various depths to the lab and measure the temperature of each sample, because this most directly measures water temperature
b. send a robot to measure the temperature of the ocean at various depths and plot the data on a graph, because ocean temperature may change with depth
c. capture fish from various ocean depths and measure the temperature of their tissues, because this directly measures the temperature of living systems
d. collect rocks from various ocean depths and determine what temperature was present during the rocks' formation, because rocks do not change once they are formed