Solve the question of and select the option from the choices A through D/E. Check your Answer and view the explanation.
War has been, throughout history, the chief _________ of social cohesion; and since science began, it has been the strongest ________ to technical progress.
n the given space of time i.e. 'throughout history' there can be only source. Reason and cause or origin can be a particular event. Boost, Encouragement and Incentive mean the same.