Pick the crystalline solid:

  • A. Cement
  • B. Ceramics
  • C. Concrete
  • D. Copper

Explanation

Copper is a metal whose atoms sit in a regular repeating lattice, so it is crystalline and melts at one sharp temperature. Cement, ceramics and concrete are amorphous or mixed materials with only short range order, so they soften over a range rather than melting cleanly. A sharp melting point is the practical test for crystallinity.

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