With no explanation, label text_A→text_B with either "not-entailed" or "entailed".
text_A: Looking out of the window , Decoud was met by a darkness so impenetrable that he could see neither the mountains nor the town , nor yet the buildings near the harbour ; and there was not a sound , as if the tremendous obscurity of the Placid Gulf , spreading from the waters over the land , had made it dumb as well as blind . . . .
text_B: The spreading did not happen
not-entailed.