20. Ceramic materials are (a) good conductors of electricity
(b) basically crystalline oxides or metals
(c) inorganic compounds of metallic and non-metallic elements
(d) none of the above
21. Which one are inorganic materials
(a) biological materials
(b) minerals and ceramics
(c) plastics
(d) Wood
22. Como​

c (diamond),

sio2 (quartz)

the volume increases

8 m/s because for him to get the same amount of energy as ray is putting out, bobby, who weighs half as much as ray, needs to run twice as fast.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.