Final answer:
In the context of natural diamond inclusions, a gas bubble is not considered a common inclusion, while a cloud, a feather, and included crystal are all types of inclusions found in diamonds.
Step-by-step explanation:
The question asks about diamond inclusions, which are internal imperfections or materials trapped inside a diamond during its formation. In the context of the given options, a gas bubble is not considered a common inclusion in diamonds. Instead, gas bubbles are typical inclusions in synthetic or imitation diamonds rather than natural ones.
Other options in the list, such as cloud, feather, and included crystal, are all known types of natural diamond inclusions. A cloud is a group of tiny pinpoints that can give a cloudy appearance to parts of the diamond. A feather is a crack or fracture within the diamond that often resembles a feather's shape. Included crystals are actual crystals of a foreign material, often another diamond, that are enclosed within the primary diamond.