Step 1: Understanding the Question:
Demography is the study of population, its size, growth, and structure. The question asks who actually coined this word, not who is called the father of the subject.
Step 2: Identify who coined the word.
The French scholar Achille Guillard coined the term 'demographie' in 1855 in his work on human population statistics. This word was later adopted into English as 'demography'.
Step 3: Why the other options are wrong.
John Graunt is often called the father of demography because he did early statistical work on birth and death records in the 17th century, but he lived long before the word itself was created, so he did not coin it. Charles Metcalfe was a colonial administrator, not a demographer. H. Spencer was a sociologist known for his theory of social evolution, not for naming this field.
Final Answer:
The term 'Demography' was given by Guillard. This is option (B).