If $f(x)=\large\frac{4^x}{4^x+2}$ then which among the following is correct ?

Question

$\begin{array}{1 1}f(x)=f(1-x) \\ f(x)+f(1-x)=0 \\ f(x)+f(1-x)=1 \\ f(x)+f(x-1)=1 \end{array}$