Which of the following is the oldest and deepest lake of the world?

The correct answer is A) Lake Baikal. Located in southern Siberia, Russia, it is the oldest lake in the world, roughly 25 to 30 million years old, and the deepest, at about 1,642 m. It is a rift lake formed by tectonic activity, and it holds about one-fifth of the world's unfrozen surface fresh water. It is a UNESCO World Heritage Site (1996).

Why the others fail:

• Lake Huron is one of the North American Great Lakes. It is large by area but nowhere near Baikal's depth or age.
• Victoria Lake in East Africa is the largest tropical lake and the largest lake in Africa by area. It is shallow, and it is geologically young.
• Lake Winnipeg in Canada is a large but shallow glacial lake.
• Chilka Lake in Odisha is a brackish lagoon on the Bay of Bengal. It is shallow and was declared a Ramsar site in 1981.

The core concept is the difference between area, depth and age of a lake. Lakes form through tectonic, glacial, volcanic or coastal processes, and these differ. This links to the Geography syllabus on lakes and to Mains questions on freshwater resources and water security.

Trap: Candidates pick Victoria, the largest by area, and confuse 'largest' with 'deepest' or 'oldest'.