Answer should be C.
As humidifier causes the air in the room to contain a greater percentage of water vapour, by turning it off would allow the air in the room to be less humid, hence the water on the floor would be easier to evaporate and the floor would dry up in a shorter amount of time. Rate of evaporation of water decreases with the moisture in the air.
Mrs Setho here. Full time Physics tutor, former teacher of DHS and VS. Hopefully, my answer should help u. 😊