Can i have an explanation for why this is d please

(someone else told me it was d)

What could explain what happened when the time was equal to 120 minutes

What is the perimeter of a rectangular building that is 80 feet wide and 140 feet deep?

Answer asap ill give ! ’ a sample of radioactive material decays over time. the number of grams, y , of the material remaining x days after the sample is discovered is given by the equation y = 10(0.5)^x. what does the number 10 represents in the equation? a. the half-life of the radioactive material, in days b. the amount of the sample, in grams, that decays each day c. the time, in days, it will take for the samples to decay completely d. the size of the sample, in grams, at the time the material was discovered