Select the FALSE statement regarding chemical$-$sensing field effect transistors.

If the gate is made positive, electrons in the base move up toward the insulating layer to create a conducting channel between the source and the drain.

The junction between the drain and the base is in reverse bias, so no current flows when a potential is applied to the source and drain.

A field effect transistor consists of a base made of p$$type Si and two regions $($source and drain$)$ of n$$type Si connected by a conductive metal gate that is separated from the base by a layer of insulating SiO$2.$

The gate potential is proportional to the logarithm of the concentration of the cation responsible for making the gate positively charged.