What is the tightly stretched membrane that forms the entrance to the middle ear called?

I'm so happy to help you with this question!! The answer is tympanic.

Explanation:

The middle ear is separated from the outer ear by the eardrum, or tympanic  membrane, a thin piece of tissue stretched tight across the ear canal. Sounds hit the eardrum, making it move.

I really hope this helps you!! :)

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.

it is b that is the answer.