What do the bohr and quantum mechanical models have in common?

In both models, electrons move around a positively charged nucleus filling different energy levels called shells.  

Explanation:

Bohr's model places electrons in ascending energy levels orbiting in a circular motion around the nucleus. The quantum mechanical model also places electrons around a positively charged nucleus following ascending energy levels, but this time these don’t move in a circular manner but instead randomly inside clouds of probability.  

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.

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