What aspect of the Schlieffen Plan is illustrated by this map?

What aspect of the Schlieffen Plan is illustrated by this map?

a. If France attacked Germany, Germany would face a war on two fronts.
b. If France attacked Russia, French troops would have to move through Germany.
c. If Russia attacked Germany, France would be too far away to offer support.
d. If Germany attacked Russia, France would be too far away to offer support.