Which of the following statements relating to Ratzel's concept of Lebensraum, is correct?

(a) It is the geographical area within which living organisms develop.

(b) It is the economic and cultural activity of the people outside their enclosed settled area.

(c). It deals with the relation between human society and a spatial organization and its physical setting.

(d). It is a geopolitical term that studies space from the viewpoint of the state.

Choose the correct option from below: