The country of Brazil & Bolivia are the pair which share a border.
The border in this context refers countries which shares a close or immediate boundary. For instance, the nation of U.S. and Canada shares a border.
Here, the pairs including "Belgium & Bulgaria", "Belize & Barbados" and "Belarus & Bangladesh" does not share a boundary.
Hence, the country of Brazil & Bolivia are the pair which share a border.
Therefore, the Option B is correct.
Missing options includes <em>"a. belgium & bulgaria b. brazil & bolivia c. belize & barbados d. belarus & bangladesh."</em>
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<em>brainly.com/question/1336648</em>