A negative crystal's crystallographic shape always mimics the habit of the host. Which of the following best describes this relationship?

• A. The host's habit
• B. The host's color
• C. Its growth rate
• D. The host's habit determines its external shape

Answer: (D)

The key idea is that a negative crystal forms inside a host crystal and its boundaries are constrained by the host’s crystal lattice and growth habit. Because the host’s crystallographic habit sets the framework and dominant faces that develop during growth, the negative crystal tends to take on a shape that mirrors that habit. In other words, the host’s habit determines the negative crystal’s external shape.

Color or growth rate don’t describe this shape-mirroring relationship, and saying only the host’s habit omits the causal link to the negative crystal’s outline.