In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the earth. Electrical circuits may be connected to ground (earth) for several reasons.
A) Calling F the intensity of the horizontal force and d the displacement of the block across the floor, the work done by the horizontal force is equal to

b) The work done by the frictional force against the motion of the block is equal to:


Part of these 105.1 Joules of work becomes increase of thermal energy of the block (

), and part of it becomes increase of thermal energy of the floor (

). We already know the increase in thermal energy of the block (38.2 J), so we can find the increase in thermal energy of the floor:

c) The net work done on the block is the work done by the horizontal force F minus the work done by the frictional force (the frictional force acts against the motion, so we must take it with a negative sign):

For the work-energy theorem, the work done on the block is equal to its increase of kinetic energy:

So, we have
This would be evaporation. Evaporation occurs when a liquid changes to a gas. Also, bonus facts:
When a gas changes to a liquid, this is called condensation. When a liquid changes to a solid, this is called freezing. When a solid changes to a liquid, this is called melting. When dry ice turns into carbon dioxide gas, this is called sublimation. Most other solids could probably do this, but dry ice is the most common example.
Answer:
D. Flexible refrigerator magnets
B. Iron cooking pans