Which of the following is a rational expression? hoose the best answer for the following questions \( \begin{array}{llll}\left\lvert\, \frac{x+1}{x^{2}+1}\right. & \text { B. } \sqrt{x}+x+1 & \text { C. } \frac{x}{x}\end{array} \)

A rational expression is a fraction where both the numerator and denominator are polynomials. In this case, option C, \( \frac{x}{x} \), is a rational expression because both the numerator (x) and denominator (x) are polynomials. However, keep in mind that \( \frac{x}{x} \) equals 1 for all x except x=0, where it's undefined, making it a special case! On the other hand, option A, \( \frac{x+1}{x^{2}+1} \), is also a rational expression because both \( x+1 \) and \( x^2+1 \) are polynomials too. The only tricky part is that \( x^2+1 \) will never equal 0 for any real number x, so this expression is defined for all real x. How cool is that?