*Question G8C11:
How are the two separate frequencies of a Frequency Shift Keyed (FSK) signal identified?*  

*Correct Answer is  D: Mark and space*  

### AI Response: (may contain errors)  

In Frequency Shift Keying (FSK), two distinct frequencies are used to represent binary data. These frequencies are known as:

- **Mark**: The frequency used to represent a binary '1'.
- **Space**: The frequency used to represent a binary '0'.

Thus, the correct answer is **D: Mark and space**.

### Explanation:

1. **Correct Answer: Mark and Space**
   - In FSK, the term "mark" refers to the frequency that represents a binary '1', and "space" refers to the frequency that represents a binary '0'. This terminology is standard in digital communication systems using FSK modulation.

2. **Why Other Choices Are Incorrect:**
   - **A: Dot and dash**: These terms are associated with Morse code, not FSK. Morse code uses dots and dashes to represent characters, not frequencies.
   - **B: On and off**: This terminology is more relevant to Amplitude Shift Keying (ASK) or simple on-off keying, where the presence or absence of a signal represents binary data.
   - **C: High and low**: While FSK does use two different frequencies, simply calling them "high" and "low" is not the standard terminology. "Mark" and "space" are the correct terms used to describe the two frequencies in FSK.

### Additional Notes:

- FSK is a type of frequency modulation where the frequency of the carrier signal is shifted between two values to encode data.
- The choice of mark and space frequencies can vary depending on the specific application or standard being used.