Draw all the plausible resonance structures of thiophene,

Here's what I find.  

Explanation:

I get the five resonance contributors shown below.

Except for the bottom structure, the S atom always has a + charge and the C atoms have a negative charge.

The resonance hybrid has six π electrons, so thiophene is aromatic.

Note that only one of the lone pairs on S is involved in the resonance system.

The other lone pair is in an sp² orbital, which is in the plane of the ring and therefore cannot participate in resonance.

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.