80 Suppose there are three functions, the first function is $y=\varphi(x)$. Its inverse function is the second function, and the graph of the third function is symmetric to the graph of the second function about the line $x+y=0$, then the third function is
A. $y=\varphi(x)$
B. $y=-\varphi(-x)$
C. $y=-\varphi^{-1}(x)$
D. $y=-\varphi^{-1}(-x)$
80 B. Let $(x, y)$ be any point on the third function graph, then $(-x, -y)$ is any point on the first function graph, thus we have
$$
-y=\varphi(-x),
$$