85 Let positive numbers $a, b, c$ satisfy $a+b+c=1, x, y, z$ be real numbers: $P=a x+b y+c z ; Q=$ $b x+c y+a z ; R=c x+a y+b z$. Then the size relationship between $P+Q+R$ and $x+y+z$ is
A. Equal
B. $P+Q+R>x+y+z$
C. $P+Q+R<x+y+z$
D. None of the above
85 A. According to the problem, we have
$$
\begin{aligned}
P+Q+R & =(a+b+c) x+(a+b+c) y+(a+b+c) z \\
& =x+y+z .
\end{aligned}
$$