Which Epidemiological Factor Related to Suicide Makes It Difficult to Determine

Which epidemiological factor related to suicide makes it difficult to determine the number of attempts that happen each year?

A) The number of suicide attempts reflects only those who enter treatment.
B) More people attempt suicide than die by suicide each year.
C) Unintentional injuries kill more people than suicide attempts each year.
D) Suicide rates consistently increased from 2000 to 2017.