Which of the following is a true statement about the map?

the border between mexico and new mexico is a thin, black line; this indicates an international boundary.
the border between california and mexico is a blue line; this indicates an international boundary.
the border between arizona and new mexico is a thin, blue line; this indicates a state boundary.
the border between arizona and new mexico is a thin, black line; this indicates a state boundary.

I will go through the answers:

The border between Mexico and New Mexico is a thin, black line; this indicates an international boundary.
- false! it's a thick black line. 

The border between California and Mexico is a blue line; this indicates an international boundary.
-false again, it's a thick black line. 

The border between Arizona and New Mexico is a thin, blue line; this indicates a state boundary.
-almost, it's a thin line, yes, but it's not blue, it's black~!

The border between Arizona and New Mexico is a thin, black line; this indicates a state boundary.
-correct: it's a thin line, and it's a state boundary, correct!

The correct answer to the question is B