Four different positions of the same dice are shown below. Find the number on the face opposite the face showing 4.

We can see that in the first and the last configuration, we are shown two corners both of which have 2 and 3, and the other side is occupied by 4 and 1 in some order. 

Two adjacent faces only share one edge and two corners.

From this we can deduce that 4 and 1 would be on the opposite faces. 

We can use the other clues to figure out the complete configuration of the cube, and open it to get the following faces:

We can see that face 1 is opposite 4. 

Therefore, Option D is the correct answer.