Two Radioactive Isotopes,X and Y,both Decay to Stable Products

Multiple Choice

Two radioactive isotopes,X and Y,both decay to stable products.The half-life of X is about a day,while that of Y is about a week.Suppose a radioactive sample consists of a mixture of these two nuclides.If the mixture is such that the activities arising from X and Y are initially equal,then a few days later the activity of the sample will be due

A) predominantly to Y.
B) predominantly to X.
C) entirely to Y.
D) to X and Y equally.