Answer: Option C. -> Making the surfaces more irregular
:
C

Friction can be increased by making the surface irregular. By using lubricants or powder between the surfaces, friction is reduced. Ball bearings use rolling friction instead of sliding friction. As rolling friction is less than sliding friction, friction is reduced. However, making irregularities on the surface increases roughness. As a result of this, friction is increased.

Answer: Option C. -> contact force
:
C

Friction is a type of contact force. Contact forces are those forces which necessarily require a physical contact. Friction cannot act between two surfaces if they are not touching each other.

Answer: Option B. -> False
:
B

By applying lots of lubricants between two surfaces, we can reduce friction. However, friction can never be entirely eliminated. Some irregularities always remain on the surfaces.

Answer: Option C. -> Both the statements are correct.
:
C
Friction is caused by the interlocking of irregularities present on the surfaces in contact. Rough surfaces have a large number of irregularities and generally have more friction.
This frictional force increases if the two surfaces are pressed harder. For example, one can easily drag a mat when nobody is sitting on it.  However, dragging the same mat becomes quite difficult when a person is sitting on it. Thus, both the statements are correct.

Answer: Option B. -> False
:
B

Since rolling friction is less than sliding friction, it is easier to roll a body than to slide (drag) it along a surface. Thus, the given statement is false.

Answer: Option A. -> Interlocking of irregularities present on the surfaces
:
A

Friction is caused by interlocking of irregularities present on the surfaces in contact. Rough surfaces have larger irregularities while smoother surfaces have lesser irregularities. Hence, rough surfaces offer more friction as compared to smooth surfaces. Even surfaces that appear smooth have numerous minute irregularities present on them. 

Answer: Option B. -> Frictional force produces heat.
:
B

Friction can produce heat. This can be observed if you rub your palms against each other. Likewise, when a meteor enters Earth's atmosphere, air applies a frictional force (air drag) against its motion. Due to this, heat is produced and the meteor starts burning.

Answer: Option D. -> Drag
:
D

Frictional force exerted by fluids, i.e., liquids and gases on objects moving through them is known as "drag". It is the force which opposes motion of any object moving with respect to the surrounding fluid.

Answer: Option A. -> True
:
A

The given statement is true. Ball bearings are used in many machines to utilize rolling friction instead of sliding friction between moving parts. Rolling friction is preferred as it is less in magnitude than sliding friction and hence improves efficiency of the machine.

Answer: Option B. -> Sohit will have to apply a larger force.
:
B
Frictional force depends on the force with which the surfaces are pressed against each other. Heavier the object, more will be the pressing force and more will be friction. This will require  a larger force to overcome friction. As Sohit is pushing a heavier box on the same surface, he will have to apply a larger force.