Concept:For a square root function g(x) to be defined, the expression inside the root must be non-negative: g(x)≥0. The domain of a sum of functions is the intersection of the individual domains of the functions.Explanation:Given f(x)=x−1+6−x, both square root terms must be defined for the same value of x.For x−1, we require x−1≥0.This simplifies to x≥1.For 6−x, we require 6−x≥0.This simplifies to x≤6.Both conditions must hold together, so x must satisfy x≥1 and x≤6.Combining these inequalities gives 1≤x≤6.This means the permissible values of x form the closed interval from 1 to 6.Answer:The domain of f(x) is [1,6].Therefore, the correct option is Option B: [1,6].