Answer:
The half-life of a radioactive isotope is the time such that the initial amount of the isotope is reduced to its half.
Thus, if we start with A grams of a given radioactive isotope, after a 1 half-life, we will have A/2 grams of the radioactive isotope.
In this case, we know that the sample has 110g of a radioactive isotope.
Then, after 1 half-life, we should have half of 110g, which is:
110g/2 = 55g
Then we should have 55 g of a radioactive isotope.
The answer that is closer to this result is option d (50 g), so that is the correct one.
