The correct answers are A) a shared history and heritage, C) commonly held customs and traditions, E) respect for certain ideals and practices, and F) a dominant language spoken for most people.
A national identity includes all of the mentioned above.
National identity is the proud sense of belonging to a country, nation or race. It is the element that unites people under with flag, one territory and all the culture, history, and traditions that it represents. It could be the language spoken in the same territory. Is the sense of recognition of values and customs that makes you love your nation, regardless of your social class or status. That is why people love their country and show it every time they can in festivities, sports contexts or tragic moments.