How small is an atom. Write down the calculation. The diameter of a US penny is 19 mm. The diameter of a silver atom, by comparison, is only 2.88 *10 -10mm.
How many silver atoms could be arranged side by side in a straight line at diameter of a penny (d penny)? 10 min

d penny =19mm I # Ag = d penny /d Ag atom I # Ag=19mm /2.88 *10 -10mm = 6.6*106 atoms
d Ag atom =2.88 *10 -10mm [ 6 600 000 atoms]
# Ag atoms--->? Atoms

the answer would be c

where are the choice options?

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.