The Term "Primary" in the Diagnosis of Primary Insomnia Refers

The term "primary" in the diagnosis of primary insomnia refers to the fact that

A) the person has never been diagnosed with insomnia before.
B) the sleep disturbance is not due to another medical or psychiatric condition.
C) the sleep disorder is a primary cause of other medical or psychiatric conditions that the individual is experiencing.
D) other sleep disorders generally follow a diagnosis of primary insomnia.