*Question T9A04:
What is a disadvantage of the short, flexible antenna supplied with most handheld radio transceivers, compared to a full-sized quarter-wave antenna?*  

*Correct Answer is  A: It has low efficiency*  

### AI Response: (may contain errors)  

The correct answer to the question is **A: It has low efficiency**. Let's break down why this is the case and examine the other choices.

### Explanation of the Correct Answer:
- **Low Efficiency**: Short, flexible antennas, such as those typically supplied with handheld transceivers, are often not resonant at the desired frequency. This results in a mismatch between the antenna and the radio, leading to lower radiation efficiency. A full-sized quarter-wave antenna is designed to be resonant, which maximizes its efficiency in radiating the transmitted signal.

### Explanation of the Incorrect Choices:
- **B: It transmits only circularly polarized signals**: 
  - This statement is incorrect because the polarization of an antenna depends on its design and orientation. A short, flexible antenna can transmit both vertically and horizontally polarized signals, depending on how it is used. A quarter-wave antenna can also be designed for either polarization.

- **C: It is mechanically fragile**: 
  - While short, flexible antennas may be more prone to bending or breaking compared to sturdier, full-sized antennas, this is not a fundamental disadvantage related to their performance. Mechanical fragility is a practical concern but does not directly affect the antenna's efficiency or effectiveness in transmitting signals.

- **D: All these choices are correct**: 
  - Since only choice A is correct, this option is also incorrect. Not all the statements provided are valid disadvantages of short, flexible antennas.

### Summary:
- The main disadvantage of short, flexible antennas is their low efficiency due to being non-resonant at the operating frequency. This results in poorer performance compared to full-sized quarter-wave antennas, which are designed to be resonant and efficient.

### Useful Rule of Thumb:
- A quarter-wave antenna is typically about $L = \frac{468}{f}$ (in MHz) for its length in feet, where $f$ is the frequency of operation. This formula helps in understanding the size and efficiency of antennas.