About 71 percent<span> of the Earth's surface is water-covered, and the oceans hold about </span>96.5 percent<span>of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers</span>
Answer:Geographic featured that acted as norther borders of the Roman Empire at its height were: Rhine River, Danube River, Carpathian Mountains, and the Black Sea.
