-- selfies with both people in it
-- wedding photos
-- boy-and-his-dog snapshots
-- some graphs
All except C, feelings are not physical.
if it is heat flow through a metal, it would be necessary to have a conductor so that the electrons can flow through it (delocalised electrons).
In terms of radiation, it would require a good absorber of heat (e.g. a black surface) so that the thermal energy flows through on the surface area.
Answer:
Efficiency can be increase by using rollers in conjunction with the inclined plane. Wedge. The wedge is an adaptation of the inclined plane. It can be used to raise a heavy load over a short distance or to split a log