5. There are 100 dice on a glass table, arranged in a $10 \times 10$ pattern, and the faces that touch between any two dice show the same number. The top and bottom faces of these 100 dice are visible, and the front, back, left, and right faces, totaling 40 faces, are also visible. Figure 4 shows a diagram of the unfolded faces of a die.
If the numbers on the 240 visible faces are summed, the maximum possible sum is ( ).
(A) 840
(B) 880
(C) 920
(D) 1240
(E) 1440
5. C.

Notice that the sum of any pair of opposite faces on a die is 7. Therefore, the total sum of the numbers on the top and bottom faces is
$$
7 \times 100=700 \text {. }
$$

Now consider the side faces.
On one hand, even if all side faces are 6 (which is impossible), the sum of the numbers would be $6 \times 40=240$, so the total sum of the numbers would be less than $700+240=940$. On the other hand, it is at least possible to have 20 points on one pair of opposite faces all being 6, and 20 points on another pair of opposite faces all being 5, so the sum of the numbers on the side faces is no less than $11 \times 20=220$, and the maximum total sum is no less than $700+220=920$.
Upon inspection, only option $\mathrm{C}$ meets the requirement.