At Which of the Following Values Of $x$ Do the Graphs Of

At which of the following values of $x$ do the graphs of $y=25+\frac{1}{2} t$ and $y=25+\frac{1}{2} t-2 \cos \left(\frac{t}{2}\right)$ intersect?

A) All multiples of $\pi$
B) All even multiples of $\pi$
C) All odd multiples of $\pi$
D) None of the above