Most country borders meet at least one country tripoint: not all of them though. For example this is always the case if one of the countries is one that borders one other country only. Can you find all combinations? Country A comes before Country B in alphabetical order. Next to each answer you are shown the number of bordered country as a hint under '# b' column. Answers are sorted alphabetically by country A.
Basically you have to look for borders that go from one sea to the other without meeting any other border on the way, or borders that are a 'circle' meeting no other borders
Oversea borders and enclaves are NOT considered
Highlighted rows indicate that both countries border at least 3 other countries