Please Read the Clinical Scenario, and Then Answer the Question

Please read the clinical scenario, and then answer the question that follow to become familiar with the traditional NCLEX question format.
An 18-month-old male is admitted to the hospital with symptoms of a respiratory infection. The patient’s mother reports that since birth, the toddler has frequently had a cough and copious nasal secretions. His weight gain has been poor, despite adequate oral intake. The patient appears in moderate respiratory distress, so oxygen therapy and IV fluids are initiated. The physician orders tests for cystic fibrosis due to the patient’s history and clinical presentation. When the tests confirm the diagnosis, as the RN, you provide education to the mother regarding this autosomal recessive disease.
-You educate the patient's mother that the most common cause of cystic fibrosis is a deletion of three nucleotides.Which of the following statements,by the mother,demonstrates an understanding of the disease?

A) "My child's disease is caused by a missing chromosome."
B) "My child's disease is caused by a missing gene."
C) "My child's disease is caused by a missing amino acid."
D) "My child's disease is caused by an infectious process."