4. Let the average of $a, b, c$ be $M$, the average of $a, b$ be $N$, and the average of $N, c$ be $P$. If $a>b>c$, then the relationship between $M$ and $P$ is ( ).
(A) $M=P$
(B) $M>P$
(C) $M<P$
(D) Uncertain
4. B.

Notice,
$$
\begin{array}{l}
M=\frac{a+b+c}{3}, N=\frac{a+b}{2}, \\
P=\frac{N+c}{2}=\frac{a+b+2 c}{4} .
\end{array}
$$

Then $M-P=\frac{a+b-2 c}{12}>0 \Rightarrow M>P$.