Let's understand the question first. We are asked about the modern term "Hertz" and what it represents.
1. Identify the options:
- Option A: pitch.
- Option B: changes per second.
- Option C: cycles per second.
- Option D: cycling.
2. Recall the definition of Hertz:
- Hertz (abbreviated as Hz) is the unit of frequency in the International System of Units (SI).
- One Hertz represents one cycle per second.
3. Match the definition to the provided options:
- Option A (pitch) refers to the perceived frequency of sound, which is not a precise definition of Hertz as a unit.
- Option B (changes per second) is not specific and can be misleading as it doesn't define the precise context of 'cycles.'
- Option C (cycles per second) accurately matches the definition of Hertz.
- Option D (cycling) is too vague and does not refer to a specific measurable concept related to frequency.
4. Determine the correct answer:
- The correct completion, representing "Hertz" accurately, is "cycles per second".
- In the list of options, "cycles per second" is listed as Option C.
Therefore, the modern term "Hertz" means "cycles per second". The correct answer is 3, since C is the 3rd option.
