Find the Missing Digit: Making ?321 Divisible by 3

To solve this problem, we'll follow these steps:

• Step 1: Observe the given number $?321$ and identify the digits we have: 3, 2, and 1.
• Step 2: Sum these digits: $3 + 2 + 1 = 6$.
• Step 3: Add the digit represented by "?", which gives us $6 + ?$.
• Step 4: Find the digit "?" such that the sum $6 + ?$ is divisible by 3.

Now, let's proceed with the calculation:

We need to select a digit from 0 to 9 that makes $6 + ?$ a multiple of 3.

Checking each option:

• $? = 0$: $6 + 0 = 6$ (divisible by 3)
• $? = 1$: $6 + 1 = 7$ (not divisible by 3)
• $? = 2$: $6 + 2 = 8$ (not divisible by 3)
• $? = 3$: $6 + 3 = 9$ (divisible by 3)
• $? = 4$: $6 + 4 = 10$ (not divisible by 3)
• $? = 5$: $6 + 5 = 11$ (not divisible by 3)
• $? = 6$: $6 + 6 = 12$ (divisible by 3)
• $? = 7$: $6 + 7 = 13$ (not divisible by 3)
• $? = 8$: $6 + 8 = 14$ (not divisible by 3)
• $? = 9$: $6 + 9 = 15$ (divisible by 3)

Therefore, from the choices given, the correct digit is $\boldsymbol{9}$ since it is provided as an option.

Thus, the complete number that is divisible by 3 without a remainder is $\boldsymbol{9321}$.