Why does the basic problem of choice arise?

A detailed answer to this question would start by defining and explaining the economic term - scarcity and establishing the relationship between our infinite needs and wants and finite resources. This would then to linked to opportunity cost which was to be defined - the foregoing of something (land, capital etc) in order to have something else - and how it gives rise to choice. 

Essentially the answer should say that the lack of unlimited resources means that something has to be foregone thus leading to choice.