Cairo is the most populous
yes he is
If you ask me its either google, hotmail, or MOST LIKELY yahoo.
The Most Popular Breed of Dog in the World is the Labrador Retriever.
It is a matter of personal opinion
English is, because a lot of people all over the world speak it and it is taught everywhere.
The Catholic Religion is the most common religion in Peru.
The religion with the most flexible rules is the religion where the only question asked is "what is the religion with the most flexible rules?" and the questions "what religion is true?" or "what religion will grant salvation?" are ignored.
The most... what? As of 2014, the religion with most followers worldwide is Christianity.
The most concentrated religion in the world is in England or the USA. The religion is Christianity.
Christianity is the most dominant religion.
The most common religion in Libya is Islam.