19. A cube with an edge length of 3 inches is composed of 27 unit cubes, of which, 21 are red unit cubes and 6 are white unit cubes. If the surface of the large cube is to have as few white unit cubes as possible, then the area of the white part on the surface of the large cube as a fraction of the total surface area of the large cube is ( ).
(A) $\frac{5}{54}$
(B) $\frac{1}{9}$
(C) $\frac{5}{27}$
(D) $\frac{2}{9}$
(E) $\frac{1}{3}$
19. A

To minimize the white area, one white unit cube can be placed at the center of the larger cube, and the other five white unit cubes can be placed at the centers of any five faces of the larger cube. The surface area of a larger cube with an edge length of 3 is $6 \times 3^{2}$ $=54$, so the white area on the surface accounts for $\frac{5}{54}$ of the entire surface area.