Which of the following correctly rounds a number to the nearest integer?

The function round() is designed specifically to round a floating-point number to the nearest integer. In the example of round(2.8), it evaluates to 3 because 2.8 is closer to 3 than to 2. This behavior of giving the nearest integer is fundamental to how the round() function operates in Python.

In contrast, the other functions listed serve different purposes. The truncate() function would reduce the number to its integer part without rounding, effectively giving you 2 when applied to 2.8. Similarly, the floor() function returns the largest integer less than or equal to the number, which in this instance would still be 2. On the other hand, the ceil() function would yield the smallest integer greater than or equal to the number, resulting in 3 for 2.8, but it does not round it in the traditional sense; it simply finds the next integer. Thus, the use of round() is what correctly fulfills the requirement of rounding a number to the nearest integer.