Given
The number of red balloons is 5.
The number of blue balloons is 7.
The number of yellow balloons is 12.
Explanation
To find the probability of randomly selected a yellow balloon
[tex]P=\frac{number\text{ of red balloons}}{total\text{ number of balloons}}[/tex][tex]\begin{gathered} P=\frac{12}{5+7+12} \\ P=\frac{12}{24} \\ P=\frac{1}{2} \end{gathered}[/tex]
Answer
Hence the correct option is C that is 1/2.
