"If France attacked Russia, French troops would have to move through Germany." is false, since the troops could move through Italy, Austria or go by sea.
"If Russia attacked Germany, France would be too far away to offer support." is false since France is right next to Germany.
"If Germany attacked Russia, France would be too far away to offer support." is false for the same reason, France is right next to Germany.
So the correct one is:
"If France attacked Germany, Germany would face a war on two fronts." because Germany was between both France and Russia.