Final answer:
The question does not provide sufficient information to determine the half-life of the substance; it only gives the initial amount (80 mg) without any time or remaining amount data. Therefore, the correct answer is d) 80mg.
Step-by-step explanation:
To determine the half-life of a substance, we need information about the time it takes for half of the substance to decay or information on the remaining amount of substance after a certain time period. The question provided does not give enough data to calculate the half-life since it only tells us the initial amount of the substance (80 mg).
To calculate the half-life, we would typically use either the formula relating the number of half-lives to time and the initial and final quantities of the substance or determine the number of half-lives by dividing the total time of decay by the half-life.
In the examples provided, such as the decay of iodine-131 or Ac-225, the initial amount, the remaining amount after a certain time, and often the half-life are given to find the remaining quantity or time.
However, without additional information about the time of decay or the remaining amount after that time, we cannot answer the original question about the half-life with the choices given.