Answer:
Christianity!
Explanation:
Ireland was (and is) a very catholic country. Legend has it that St Patrick explained the Holy Trinity using a Shamrock and brought Catholicism to Ireland. Paradoxically, St Patrick was British. Celebrating St Patrick's is both a Catholic and Irish thing to do but with the years has become more of a laic celebration on the surface.
The answer is 4,132 miles if you are talking about the Nile river.
B. Govern themselves using agreed upon laws
Answer:
Emperor Claudius was the first