Question: Which of the following is a characteristic of harmonic progressions?

Options:

1. They can only contain positive numbers.
2. They can be represented graphically as a straight line.
3. The difference between consecutive terms is constant.
4. The sum of the first n terms can be calculated easily.

Correct Answer: They can only contain positive numbers.

Solution:

Harmonic progressions can contain negative numbers, but the terms themselves must be positive to maintain the definition of harmonic sequences.