Scientists have determined that Radon - a colorless, odorless, and tasteless gas - is unstable because of its radioactive nature and continuously decays into Progeny. Since it has been proven that there was no Progeny at the time of earth’s formation, one can accurately estimate earth’s age by determining the increase in Progeny in earth’s atmosphere over the last 200 years and using it to determine how many years it would have taken to reach current levels of Progeny.

The answer to which of the following questions would be most important in determining whether using the method would help in achieving the stated objective?

A. Whether the rate of decay of Radon into Progeny is different during day time and night time?
B. Whether Progeny is stable or gets converted into some other gas at constant rate?
C. Whether there have been any changes in the atmosphere in the past century that have increased the radioactivity decay level of all gases?
D. Whether there are methods, better than the method given, to estimate the earth's age?
E. Whether amount of Radon or Progeny varies from region to region?


OA C

Source: e-GMAT