5. (10 points) The total value of 12 coins is 90 cents, consisting only of 5-cent and 10-cent coins. How many of each type are there?
A. 4
B. 5
C. 6
D. 7
【Answer】Solution: The number of 5-fen coins:
$$
\begin{aligned}
& (12 \times 1-9) \div(1-0.5) \\
= & 3 \div 0.5 \\
= & 6 \text { (pieces); }
\end{aligned}
$$
The number of 1-jiao coins: $12-6=6$ (pieces).
Answer: Each type of coin is 6.
Therefore, the correct choice is: $C$.