The independent variable is; A: The number of secounds.
The dependent variable is; B) The number of feet the sub descends.
A dependent variable depends on another variable in a given data while an independent variable does not depend on any other variable.
We are told that the submarine is descending at a rate of 7 ft/s. Now, this means that for every second, he descends at a rate of 7ft. Thus, the more the number of seconds, the more the distance covered.
Thus, the number of feet depends on the time taken in seconds and such the independent variable is the the number of seconds while the dependent variable is the number of feet the sub descends.
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