Explain why a construction worker who uses a jackhammer on a rock does not produce a metamorphic rock.

Using a jackhammer on a rock does not change its structure, just breaks it into smaller pieces. Changing the crystalline structure requires partial or complete melting of the rock (must be hot enough to allow atomic rearrangement

Efficiency is an action of doing something. for example when you take a test. good efficiency means you did well but bad effeciency or no effiency means you did bad.