Final answer:
A number will round to 500 when it is between 450 and 549. Among the options provided, 450 and 500 round to 500, while other options do not.
Step-by-step explanation:
When rounding a number to the nearest hundred, we look at the tens digit. If it's 5 or greater, we round up to the next hundred. If it's 4 or less, we round down. To become 500 when rounded to the nearest hundred, the number has to be in the range of 450 to 549. This is because any number from 450-499 would round up to 500, and any number from 500-549 would round down to 500.
Looking at the options provided:
A) 600 would round to 600.
B) 550 would round to 600.
C) 450 would round to 500.
D) 500 is already at the hundred and remains unchanged.
Therefore, the numbers that can be 450 (option C) and 500 (option D).