Which strategy did the allied powers attempt in World War 1 to establish direct communication between the western and eastern fronts

For some 30 years after 1870, considering the likelihood of another German war, the French high command had subscribed to the strategy of an initial defensive to be followed by a counterstroke against the expected invasion: a great system of fortresses was created on the frontier, but gaps were left in order to “canalize” the German attack. France’s alliance with Russia and its entente with Great Britain, however, encouraged a reversal of plan, and after the turn of the century a new school of military thinkers began to argue for an offensive strategy. The advocates of the offensive à l’outrance (“to the utmost”) gained control of the French military machine, and in 1911 a spokesman of this school, General J.-J.-C. Joffre, was designated chief of the general staff. He sponsored the notorious Plan XVII, with which France went to war in 1914.

Explanation:

basically: Plan XVII

the answer is option a.