Final answer:
Lake Tanganyika is the longest and second-deepest African lake, spanning across four countries and reaching a depth of 1,470 meters.
Step-by-step explanation:
The African lake that is both the longest and second deepest in the world is Lake Tanganyika. It stretches across four countries: Tanzania, Democratic Republic of the Congo, Burundi, and Zambia. It is approximately 676 kilometers long and has a maximum depth of about 1,470 meters.
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