What type of border would likely have the most protection?
a. state
b. province
c. national
d. city

The correct answer is A. State.

Explanation

A border is a limit that divides two territories of different nature, the borders divide different territorial entities such as continents, countries, cities, states, departments, neighborhoods, private properties, among others. However, the borders that have greater protection and security presence are the borders of the countries, because governments want to maintain their state sovereignty throughout the national territory and this is one of the most common actions worldwide. So, the correct answer is A. State