Answer:
a. a biological organism.
Step-by-step explanation:
Herbert Spencer -
Herbert Spencer has his hands on various fields , he is known to be sociologist , anthropologist , English philosopher and the prominent classical liberal political theorist during the Victorian era .
Being a sociologist as well as a biologist , he mixed both the field , in order explain the system of the society , by comparing the society to the biological organism .
Hence , from the question,
The correct option is a. a biological organism.