30. As shown in the figure, it is a cube, with the six faces labeled $1, 2, 3, 4, 5, 6$. The face with 1 is opposite to the face with 6, the face with 2 is opposite to the face with 5, and the face with 3 is opposite to the face with 4. Initially, the face with 6 is facing down. The cube is rolled along the table, and the number facing down is recorded each time (starting with 6). After 5 rolls, the recorded numbers are exactly $1, 2, 3, 4, 5, 6$ once each. How many different sequences of these 6 recorded numbers are there?
A. 36
B. 40
C. 48
D. 60
【Solution】Solution: The first number is 6. If the second number is 2, then:
If the third number is 1, the last three numbers have 2 possibilities: 354 and 453;
If the third number is 3, the last three numbers have 4 possibilities: 145, 154, 514, 541;
If the third number is 4, similarly (symmetrical to 3), there are 4 possibilities;
In total, $2+4+4=10$ possibilities; $\square$
If the second number is 3, 4, or 5, similarly to 2, there are 10 possibilities each, totaling $10 \times 4=40$ possibilities. Therefore, the answer is: $B$.