The question asks for the least number that can be formed using the digits 3, 5, 1, 2, and 4.

To create the smallest possible number, we need to arrange the digits in ascending order, i.e., from the smallest to the largest. The correct order would be: 1, 2, 3, 4, 5.

So, the smallest number you can form with these digits is 12,345.

Among the options, 12,345 is the correct answer.

Would you like more details or have any other questions? Here are five related questions for further exploration:

1. How do you find the largest number from a set of digits?
2. What is the difference between ascending and descending order?
3. Can you form the least number if the digits include zero?
4. How would the process change if repetition of digits were allowed?
5. How would you compare two numbers to determine which is smaller?

Tip: When trying to form the smallest number from a set of digits, always start with the smallest non-zero digit!