Final answer:
The correct option is a. Mineral habit is the typical shape a mineral grows into when it has sufficient space, reflecting the mineral's crystalline structure and environmental conditions of formation.
Step-by-step explanation:
The term mineral habit refers to the characteristic external shape displayed by minerals. The best description of mineral habit is: The shape a mineral grows into, given sufficient space. This aspect of minerals is an outcome of the inherent crystal structure that defines how the atoms are spatially arranged.
Foremost, a mineral is defined as a naturally occurring, inorganic solid with a definite chemical composition and a characteristic crystalline structure. In cases where the growth space for the mineral is unrestricted, the mineral will likely form into its typical shape, known as its habit. However, if the space is limited, the mineral may develop different forms, influenced by the available space. The habit of a mineral can provide insights into the environment of formation and is useful for identification purposes.