Unit Digit Problem: Finding Numbers Ending in Zero

Select a number whose unit digit is 0.

Let's solve the problem step by step:

• Step 1: Identify the numbers provided in the choices. The numbers are $7$, $90$, and $10$.
• Step 2: Check each number to see if its unit digit is zero.
  - For $7$: The unit digit is $7$, which is not zero.
  - For $90$: The unit digit is $0$, which meets the criteria.
  - For $10$: The unit digit is $0$, which also meets the criteria.
• Step 3: According to these findings, both $90$ and $10$ have unit digits of zero.
• Step 4: The correct choice that reflects our findings is the option stating, "Answers (b) and (c)," which corresponds to $90$ and $10$.

Therefore, the solution is Answers (b) and (c), as both numbers have a unit digit of zero.