Answer:
The answer is B -The border between Alaska and British Columbia is a thick line, indicating a national border.
Explanation:
Alaska is a state in the USA. British Columbia is a Canadian province. Therefore, it shares a national border and is indicated by a thick line on the map.
The boundary between New Mexico and Texas is a state boundary as they are both US states.
Haiti and The Dominican Republics, while being on the same island, are not the same country. So they are divided by a national boundary.
North Dakota and South Dakota do have a state boundary between them. However, it is indicated by a thin line.