Answer:C. [tex]\sqrt{x}+3=13[/tex]Step-by-step explanation:We know that,A radical equation is the equation in which the variable is under the radical.According to the options, we see that,In the equation [tex]\sqrt{x}+3=13[/tex], the variable is under the radical.All other equations have constant number under the radical.Thus, we get,Equation C i.e. [tex]\sqrt{x}+3=13[/tex] is a radical equation.