The addressee might give feedback using manual and/or nonmanual signals. The responses might be in the form of affirmation or rejection. It might also be a very short clarification question or an indication of occurrence of misunderstanding. Typical back-channeling signals in DGS are nonmanual signals like nose-wrinkle, a slight head nod, and manual signals like palm_up, right++, yes++, no++.
a. right ++
b. yes ++
c. no ++