Question

Heat transfer by conduction occurs when
molecules
(1) flow as currents through liquids
(2) form waves that travel through space
(3) become less dense and rise

Answer 1

It is none of the three. Conduction occurs when a heat source directly is touching an object. 

Explanation: Number 1 is convection. Key term: convection currents. Number 2 is radiation, as radiation can pass through space. Number 3 is just explaining a part of the convection current.

Answer 2

None of above.
Hope it helps! :D