PLEASE HELP RIGHT AWAY!! THANK YOU :) Copper turns a green-brown when it is exposed to oxygen in air. What chemical property of oxygen causes this effect?

A). its reactivity

B). its mass

C). its flammability

D). its volume

The answer is option A.

its reactivity

I hope this helps you.

space exploration has led to the development and technological improvement of many everyday items. (if this answer is wrong i will find the right answer) : )

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.