Answer: Social-cultural system
Step-by-step explanation:
Social-cultural system is the system that is made from the collection of social structures, social concepts, parts of interaction, emotional feature etc in which human being are dependent on each other for their functioning. People in socio-culture are based on the system, society and cultural factor to work as the whole system.
Thus, social -cultural system is the part of sender that impact on encoded message's information or content.
Other option are incorrect because environmental factor, political factor and volume are not the components involved in the encoded message or the content of the message.