The statement that is true of an organ is: "Organs must have large pipes."
However, it's worth noting that while traditional pipe organs do have large pipes, there are also smaller organs, such as console organs or digital organs, which may not have large pipes, but they wouldn't fall under the traditional definition of a pipe organ.
The other statements are false:
- An organ is not necessarily the oldest keyboard instrument; that title might go to the harpsichord or clavichord.
- Not all organs are electronic; many are mechanical and rely on wind to produce sound.
- Organs have a wide range of sound, especially larger pipe organs that can produce a vast array of tonal colors and dynamics.