In which situation is the speed of the car constant while its velocity is changing? The car travels down a straight track at 30 m/sec.
The car travels around a circular track at 30 m/s.
The car begins from rest and accelerates to 20 m/s.
The car begins traveling at 30 m/s and decreases to 15 m/s.

it is a good conductor

explanation:

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.