Which statement correctly describes three common CAD assembly constraints and their effect?

• A. Mate fixes positions permanently; Flush makes surfaces non coplanar; Align rotates parts randomly.
• B. Mate aligns parts' faces/axes; Flush makes planar surfaces coplanar; Align matches orientation.
• C. Flush aligns axes; Mate scales parts; Align creates new components.
• D. Mate duplicates parts; Flush creates gaps; Align removes constraints.

Answer: (B)

Understanding how three common CAD assembly constraints control how parts relate in an assembly helps you model precise relationships between components. A mate constraint is used to bring two features together by aligning faces, edges, or axes so they meet or become coaxial; this is how you fix the relative position of parts. A flush constraint makes planar surfaces coplanar and flush against each other, ensuring these surfaces lie in the same plane and contact each other. An align constraint sets the orientation of parts so that their features or coordinate systems point the same way, effectively matching their orientation.

These descriptions fit typical CAD behavior: mates define position by contact or coaxial alignment, flush ensures surface-to-surface contact in the same plane, and align controls how the parts are oriented relative to one another. The other options mix up what each constraint does—for example, mate isn’t about permanently locking a position, flush isn’t about making surfaces non-coplanar, and align isn’t about random rotation or creating new components.