Which of the following substances is a fluid?
air
ice
sand
candles

Air

Explanation:

Air like all gasses, is a liquid. Liquid is a substance that flows freely. Therefore, your answer would be gas.

(1) Though Ice, can melt to become a liquid, its form is still TECHNICALLY a solid.

(2) Sand can form to shape, but it still considered a solid. Sand is a solid because each grain of sand is just a very small solid that can hold its shape

(3) Candles, are a solid even though, like ice, can become a liquid but only for a short amount of time because wax would eventually turn back into a solid.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.