Step 1: Concept
Properties of right-angled triangles.
Step 2: Analysis
Check if $7^2 + 24^2 = 25^2 \implies 49 + 576 = 625$. It is a right-angled triangle.
Step 3: Calculation
In a right-angled triangle, the circumradius ($R$) is half of the hypotenuse.
$R = 25 / 2 = 12.5$.
Step 4: Conclusion
The circumradius is 12.5.
Final Answer: (A)