Which solid conducts electricity most efficiently?
potassium chloride
sugar
graphite
silver

Option (c) is the correct answer.

Explanation:

Graphite is an allotrope of carbon atom. Also, being a solid it is able to conduct electricity due to the presence of free or mobile electrons.

Whereas in solid form potassium chloride, sugar and silver cannot conduct electricity as there are no free electrons present.  

Thus, we can conclude that out of the given options, graphite is the solid which conducts electricity most efficiently.

mechanics (greek   is that area of science concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. the scientific discipline has its origins in ancient greece with the writings of aristotle and archimedes[1][2][3] (see history of classical mechanics and timeline of classical mechanics). during the early modern period, scientists such as galileo, kepler, and newton laid the foundation for what is now known as classical mechanics. it is a branch of classical physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. it can also be defined as a branch of science which deals with the motion of and forces on objects. the field is yet less widely understood in terms of quantum theory.

explanation:

it is the most commonly accepted one