Despite a full one hour meeting, they could not arrive at any consensus.

Answer: Option D

Union : the action of joining together or the fact of being joined together, especially in a political context.
Unity : the state of being united or joined as a whole.
Harmony : the combination of simultaneously sounded musical notes to produce a pleasing effect.
Agreement : harmony or accordance in opinion or feeling.
Consensus : a general agreement.

Synonym of Consensus is Agreement