5. (10 points) An old clock's minute hand and hour hand overlap every 66 minutes of standard time. Therefore, this old clock's 24 hours compared to the standard 24 hours ( )
A. is 12 minutes faster
B. is 6 minutes faster
C. is 6 minutes slower
D. is 12 minutes slower
【Analysis】The minute hand and the hour hand, except at 12 o'clock (including 24 o'clock or 0 o'clock), overlap once every hour, so they overlap 22 times in 24 hours. The old clock overlaps every 66 minutes of standard time, so the 24 hours of the old clock is $22 \times 66$ $=1452$ (minutes), while the 24 hours of the standard clock is $60 \times 24=1440$ (minutes). The difference between the two is the time this old clock is slow.

【Solution】Solution: $66 \times(24-2)$
$$
\begin{array}{l}
=66 \times 22 \\
=1452 \text { (minutes) } \\
60 \times 24=1440 \text { (minutes) } \\
1452-1440=12 \text { (minutes) }
\end{array}
$$

That is, this old clock's 24 hours are 12 minutes slower than the standard 24 hours.
Therefore, the answer is: $D$.