*Question E2B01:
In digital television, what does a coding rate of 3/4 mean?*  

*Correct Answer is  A: 25% of the data sent is forward error correction data*  

### AI Response: (may contain errors)  

In digital television, a coding rate of 3/4 refers to the proportion of data that is actual information versus error correction data. Here's how to understand it:

### Correct Answer: A
- **Explanation**: A coding rate of 3/4 means that out of every 4 bits transmitted, 3 bits are actual data, and 1 bit is used for forward error correction (FEC). This implies that 25% of the data sent is for error correction.  
  - **Calculation**:  
    - Total bits = 4  
    - Data bits = 3  
    - FEC bits = 4 - 3 = 1  
    - Percentage of FEC = $\frac{1}{4} \times 100\% = 25\%$

### Why Other Choices Are Incorrect:
- **Choice B: Data compression reduces data rate by 3/4**  
  - **Incorrect**: Coding rate does not refer to data compression. It specifically relates to the ratio of data bits to total bits, not a reduction in data rate.

- **Choice C: 1/4 of the time interval is used as a guard interval**  
  - **Incorrect**: A guard interval is a separate concept used to prevent interference between symbols in digital transmission. It is not related to the coding rate.

- **Choice D: Three, four-bit words are used to transmit each pixel**  
  - **Incorrect**: This choice describes a method of data representation, not a coding rate. The coding rate is about the ratio of data to error correction bits, not how data is structured for transmission.

Understanding coding rates is crucial for ensuring data integrity in digital communications, as it helps balance between data throughput and error correction capability.