The correct answer is: Fourth generation.
The Bodhi Vriksh in Bodhgaya is a descendant of the original Bodhi tree under which Gautama Buddha attained enlightenment. The original tree was cut down in the 11th century, but a sapling from it was planted in Bodhgaya in the 19th century. This sapling is the fourth generation of the original Bodhi tree.
The first generation of the Bodhi tree was the original tree under which Gautama Buddha attained enlightenment. This tree was cut down in the 11th century.
The second generation of the Bodhi tree was a sapling from the original tree that was planted in Bodhgaya in the 12th century. This tree died in the 19th century.
The third generation of the Bodhi tree was a sapling from the second generation tree that was planted in Bodhgaya in the 19th century. This tree died in the 20th century.
The fourth generation of the Bodhi tree is the current tree in Bodhgaya. This tree is a sapling from the third generation tree that was planted in Bodhgaya in the 20th century.
The Bodhi Vriksh in Bodhgaya is a sacred tree for Buddhists. It is a symbol of enlightenment and hope.