
- A6
- B4
- C3
- D2
Read off every face that shares a view with 3. The first die shows 3 with 2 and 6, the third shows it with 6 and 1, and the fourth shows it with 5 and 1 - so and are all adjacent to 3.
That leaves only one number unaccounted for, and a face can only be adjacent or opposite. Hence 4 is opposite 3, which is Option 2.