3. (10 points) The password for Xiao Ming's suitcase lock is a three-digit number composed of the digits 8 and 5. On a certain trip, Xiao Ming forgot the password. He needs to try at least ( ) times to ensure he can open the suitcase.
A. 9
B. 8
C. 7
D. 6
【Analysis】For the three-digit number $\square \square \square$, considering the three positions, there are two scenarios: (1) 1 five and 2 eights, in which case the position of 5 has 3 possibilities; (2) 2 fives and 1 eight, in which case the position of 8 has 3 possibilities. Therefore, there are $3+3=6$ possibilities in total, and this is the basis for the solution.

【Solution】Solution: According to the analysis, $3+3=6$ (times)
Answer: He needs to try at least 6 times to ensure he can open the box.
Therefore, the correct choice is: $D$.