'They' is a personal pronoun. With an appropriate possessive the correct option is
A. They must do his duty.
B. They must do her duty.
C. They must do its duty.
D. They must do their duty.
Answer:D
'They' is a personal pronoun. With an appropriate possessive the correct option is
A. They must do his duty. B. They must do her duty. C. They must do its duty. D. They must do their duty.