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3. Explain the difference between interstitial and self-interstitial point defects. 4. Dislocations are... a. related to extra atoms positioned between atomic sites b. caused by small atoms filling the voids of the crystal structures c. line defects that produce plastic deformation d. formed across the twin plane 5. Which of the following is false about grain boundaries: a. Small grains resist plastic deformations b. Small grains result in more uniform mechanical properties c. Susceptible to etching d. None of the above