The way in which people address each other depends on their age,

The way in which people address each other depends on their age, sex, social group and personal relationship. The English system of address forms frequently used includes first name, last name, title+last name, _______, and kin term.
A、title+first name
B、title+title
C、title alone
D、first name+last name+title
【正确答案】：C