Root

But now we just alternate strings every bass note.

So you're grabbing bass notes from the chord So here I'm going from the sixth string to the fourth string, so I'm grabbing a G, then I'm grabbing, that's the root of the chord, then I'm grabbing on the fourth string the open D, which is the fifth of the chord.

Root, fifth, root, fifth.

There are lots of variations.

You could grab root, fifth, third, fifth.