Concerning bulimia nervosa:

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: A

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: the affected protein in cystic fibrosis (CF) is the cystic fibrosis transmembrane conductance regulator (CFTR), which is a chloride channel, not a sodium channel. The other options are incorrect: (a) The commonest mutation in Caucasians is ΔF508, not ~F-580. (b) Parents of an affected child are typically carriers and do not show symptoms. (c) Prenatal diagnosis is not possible in all cases due to the vast number of mutations. (d) There are over 2000 known mutations causing CF.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.