6. A customs office received an intelligence report that a transnational drug trafficking group will hide drugs in a few boxes of a shipment entering the country, and the drug boxes are marked with a mysterious number:
$$
\overline{x 0 y z}=9 \overline{x y z} \text {. }
$$

Upon inspection, it was found that each box in the shipment has a number, and the number is a four-digit number with the hundredth digit being "0". Therefore, the drugs are hidden in the box marked with ( ).
(A) 2025
(B) 4050
(C) 6075
(D) All of the above
6. D.

Let the required four-digit number be $\overline{x 0 y z}$. Then
$$
\overline{x 0 y z}=9 \overline{x y z} \text {. }
$$

Thus, $1000 x+10 y+z=9(100 x+10 y+z)$.
Simplifying, we get $100 x=8(10 y+z)$.
From this, we know that the right side of the equation is divisible by 8.
Therefore, $x$ must be an even number: 2, 4, 6, or 8.
Clearly, $8(10 y+z) \leqslant 8 \times 99<800$.
Thus, $x \neq 8$.
When $x=2$,
$200=8(10 y+z)$
$\Rightarrow 25=10 y+z \Rightarrow y=2, z=5$;
When $x=4$,
$400=8(10 y+z)$
$\Rightarrow 50=10 y+z \Rightarrow y=5, z=0$.
When $x=6$,
$600=8(10 y+z)$
$\Rightarrow 75=10 y+z \Rightarrow y=7, z=5$.
In summary, the numbers of the three boxes containing the drugs are $2025$, $4050$, and $6075$.