Explanation

The Caspian Sea and Aral Sea are indeed lakes, not seas, despite being large and saline.

The Red Sea is a sea, as it is a part of the Indian Ocean and connected to it via straits. 

Additional Information

The Caspian Sea is the world's largest inland body of water

 It lies between Europe and Asia

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The Aral Sea was an endorheic lake

Lying between Kazakhstan to its north and Uzbekistan to its south,

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The Red Sea is between Arabia and Africa

It separates the Arabian Peninsula from northeastern Africa.