Answer
$C$
Work Step by Step
Step 1. The decay function is $y=y_0e^{-0.0241\ t}$
Step 2. Half-life means the time needed for $y=\frac{1}{2}y_0$, we have $\frac{1}{2}y_0=y_0e^{-0.0241\ t}$ and we need to solve for $t$.
Step 3. The answer is $C$