5$\cdot$18 The figure on the right shows a part of the graph of the quadratic function $y=a x^{2}+b x+c$. Based on the graph, which of the following statements is correct?
(A) $a-b+c=0$.
(B) $a-b+c>0$.
(C) $a-b+c<0$.
(D) The range of $a-b+c$ generally cannot be determined, it depends on the specific values of $a, b, c$. (China Fujian Province Junior High School Mathematics Competition, 1984)
[Solution] When $x=0$, $y=1$, then $c=1$.
When $x=1$, $y=0$, then $a+b+c=0$. And since the parabola opens downwards, we know $a<0$.
Notice that when $a=-1, b=0$, we have $a-b+c=0$. And when $a=-2, b=1$, we have $a-b+c<0$. Therefore, the answer is $(D)$.