Friction can be increased by

Friction is the resistive force that acts between two surfaces in contact and opposes their relative motion. Its magnitude depends chiefly on how rough the contacting surfaces are: rougher surfaces have more microscopic irregularities that interlock and resist sliding, while a lubricant between the surfaces fills those irregularities and lets them glide past each other more easily, lowering the resistance.

Applying this here: rough surfaces increase the number of interlocking points between the two contacting surfaces, so they raise the resistance to sliding, which is exactly what friction is. Oil and moisture, by contrast, both act as lubricants — they coat the surfaces and reduce the interlocking, so they lower friction instead of raising it.

• Applying oil: oil is a lubricant, so it smooths the contact between the surfaces and lowers friction rather than raising it.

• Moisture on the surfaces: moisture behaves the same way as oil here, coating the surfaces and reducing their interlocking, so it lowers friction rather than raising it.

• All of these: since two of the three listed methods actually lower friction rather than raise it, the claim that all of them increase friction does not hold.

So friction is increased specifically by making the surfaces rougher, which is why rough surfaces is the correct choice.