Explanation: A crystal's temperature coefficient quantifies how much its operating frequency changes per degree of temperature variation. A *low-temperature coefficient* indicates that the crystal's frequency is highly stable and will undergo only minimal shifts despite substantial changes in ambient temperature. This characteristic is crucial for applications requiring precise frequency control, such as in amateur radio transceivers and test equipment. Conversely, a *high-temperature coefficient* crystal would exhibit significant frequency drift with temperature changes, making it unstable. "Constant-temperature coefficient" is not a standard term used to describe the stability; the important factor is the *magnitude* of the coefficient – whether it's high or low – determining the extent of frequency variation. Therefore, a crystal with "very small changes in its operating frequency with relatively large temperature variations" is by definition a low-temperature coefficient crystal.