18. What is the density of a substance with a mass of 0.90 kg and a volume of 1.2 mL? 21. An oxygen tank in the lab has a pressure of 12 atm at 250C. If the pressure inside the gas tank exceeds 25 atm, the tank will explode. If a fire occurs in the lab, raising the temperature of the gas inside the cylinder to 398oC, will the tank explode?

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.

since electrons are negative the answer is neagtaive