The value that is being measured in the columns labeled "Fraction remaining" and "Percentage remaining" is (d) amount of material that has not decayed.
From the question, we understand that the chart measures the rate of decay.
So, the fraction remaining column would show the remaining amount of the material that is being measured, as a fraction.
The percentage remaining column would show the remaining amount of the material that is being measured, as a percentage.
Hence, the value that is being measured in these columns is (d) amount of material that has not decayed.
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