4. The positive integer $n$ is less than 100, and satisfies the equation $\left[\frac{n}{2}\right]+\left[\frac{n}{3}\right]+\left[\frac{n}{6}\right]=n$, where $[x]$ denotes the greatest integer not exceeding $x$. How many such positive integers $n$ are there?
(A)2
(B) 3
(C) 12
(D) 16
4. (D).

From $\frac{n}{2}+\frac{n}{3}+\frac{n}{6}=n$, and if $x$ is not an integer, then $[x]<x$, we know that $2|n, 3| n, 6 \mid n$, which means $n$ is a multiple of 6. Therefore, the number of such positive integers less than 100 is $\left[\frac{100}{6}\right]=16$.