Step 1: Conditions
\(x-1\ge0\) gives \(x\ge1\), and \(3-x\ge0\) gives \(x\le3\).
Step 2: Intersect
Both hold together only for \(1\le x\le3\), so the domain is \([1,3]\). Option (C).
Final Answer:
The domain is \([1,3]\), option (C).
\[ \boxed{\text{(C) } [1,3]} \]