An engineering company needs to solve a design problem. It is designing a high-speed train to transport passengers between Boston and Atlanta. Which statement is a constraint for this project? A. The train must have a dining car in which meals are served. B. The train must be able to carry at least 300 passengers. C. The train must cost less than $6 billion to build. D. The train must be able to complete the trip in six hours​

it would be a gas formation

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.

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.