求下列函数的函数值的算法中需要用到条件语句的函数为(   )

A：$f\left(x\right)={\text{log}}_4\left(x^2+1\right)$

B：$y=x^3-1$

C：$f\left(x\right)=\text{{}\begin{array}{c}1,x\le 2.5\\ -1,x>2.5\end{array}$

D：$f\left(x\right)=2^x$