Option 1 ( Lake Baikal ) is the right answer.
Lake Baikal is the largest (by volume) freshwater lake in the world, containing roughly 20% of the world’s unfrozen surface fresh water, and at 1,642 m (5,387 ft), the deepest. It is also among the clearest of all lakes, and thought to be the world’s oldest lake at 25 million years. It is the seventh-largest lake in the world by surface area. With 23,615.39 cubic kilometres (5,700 cubic miles) of fresh water, it contains more water than all the Great Lakes combined.