There are no options, but I hope I can help you anyway.
Channels are proteins located on the cell membrane that open or close in response to a number of stimuli, such as electric voltage changes and certain molecules, such as GABA, Sodium potassium and others. Those channels must be neutral to the "background" material of the cell, so they cannot respond to WATER IN THE EXTRACELLULAR FLUID - else they would be responding the whole time.
