Concerning Neurofibromatosis Type 1 (NF1), Which One of the Following

Concerning Neurofibromatosis Type 1 (NF1) , which one of the following statements is true?

A) Bilateral acoustic neuromas are common
B) Clinical severity in individuals is similar in a given family
C) New mutations occur rarely
D) Pigmented spots on the iris are a characteristic feature
E) The diagnosis is likely if two café-au-lait patches are present