A scientist kept 500 grams of a radioactive material in a container. After 60 minutes, he observed that 62.5 grams of the radioactive material was left in the container. Based on the observation, which of these is the most likely inference drawn by the scientist?
a. About 250 grams of the material decayed in 20 minutes.
b. About 250 grams of the material decayed in 40 minutes.
c. About 31.25 grams of the material will be left in the container after 30 minutes.
d. About 31.25 grams of the material will be left in the container after 50 minutes.
