*Question T5C13:
What is the abbreviation for kilohertz?*  

*Correct Answer is  D: kHz*  

### AI Response: (may contain errors)  

The correct abbreviation for kilohertz is **kHz**. Here's a breakdown of why this is the correct choice and why the others are incorrect:

1. **Correct Answer: kHz**
   - The abbreviation for kilohertz is formed by combining the prefix "k" for kilo (which means 1,000) with "Hz," which stands for hertz, the unit of frequency. 
   - The correct format uses a lowercase "k" followed by an uppercase "H" and an uppercase "z" to denote the unit properly.

2. **Incorrect Choices:**
   - **A: KHZ**
     - This option uses uppercase letters for both "K" and "H," which is not the standard convention. The correct format requires a lowercase "k."
   - **B: khz**
     - This option uses a lowercase "k" but incorrectly uses lowercase for both "H" and "z." The "H" should be uppercase to represent hertz correctly.
   - **C: khZ**
     - This option has a lowercase "k" and an uppercase "Z," which is incorrect. The "H" must be uppercase, and "z" should also be lowercase.

3. **Rules of Thumb:**
   - When writing unit abbreviations, follow the standard conventions for capitalization:
     - Prefixes (like kilo) are typically lowercase (e.g., "k" for kilo).
     - The unit symbols (like hertz) are typically uppercase for the first letter and lowercase for subsequent letters (e.g., "Hz").
   - Always check the standard abbreviations for units to ensure proper usage.

By understanding these conventions, you can correctly identify and use unit abbreviations in your studies and on the exam.