(A) A word showing destination/unknown direction is needed after “knew not” → “whither” (= to what place they went).
(B) A noun describing the overall tone or general meaning of remarks is needed → “tenor” (= the general drift of what he said).
(C) A term referring to the system of land ownership/holding is needed → “tenure” (= land tenure system).
(D) A verb describing plants drying up due to lack of water is needed → “wither” (= shrivel and die).