A. European countries were trying to gain as much land as possible to become super powers in the world.
Step-by-step explanation:
Considering the geopolitics of that time, the Britain, France and the USSR (now Russia) wanted to spread their power and authority as much as they can so that they can become a major super powers. This was also important as they wanted to counter the looming threat of powerful Germany and the danger of loosing Middle East to Germany. The decision to invade Middle Eastern lands was taken before the WWI and the target was the Ottoman Empire. The Sykes-Picot Agreement signed between the Britain, France and the USSR in 1916 is an example of that. As soon as the Ottoman decided to form a defensive alliance with Germany, this became an urgent matter. Hence, European countries were trying to gain as much land as possible to become super powers in the world.