What is the range of the function \(f(x)=\frac{|x|}{1+|x|}\)?

Correct answer: \([0,1)\)

Let \(t=|x|\). Then \(t\ge 0\) and \(f(x)=\frac{t}{1+t}\). At \(x=0\), we get \(t=0\) and hence \(f(x)=0\). For every finite \(t\), \(\frac{t}{1+t}<1\), so the value 1 is never attained, although the function approaches 1 as \(|x|\) increases. Therefore, the range is \([0,1)\). Option B is incorrect because 0 is included, while option C is incorrect because 1 is excluded. Exam tip: for rational functions, check both limiting values and whether each endpoint is actually attained.