Which of the Following Is a Reason Why There Isn't

Which of the following is a reason why there isn't an accurate figure on how many LGBT people are there in the United States?

A) Researchers define and measure sexual orientation in the same, standard way.
B) Respondents may not be willing to disclose this information.
C) People who engage in same-sex behavior consider themselves gay.
D) More LGBTs are willing to come out than in the past.