The answer is D. Culture is the entire way of life of a group of people, and it acts as a lens through which we view the world.
Culture is a way of life made up of beliefs, customs, values, symbols and so forth and are specific to certain people or societies. Culture influences how we behave and see the world. We are all part of a particular type of culture.
The other answers are results of some cultural beliefs and structures but they are not the defining definition of what culture is.