Prevented by folic acid

Correct Answer: B

Rationale: Spina bifida is a neural tube defect (NTD) preventable by periconceptional folic acid, reducing incidence by 50-70%, per CDC evidence. It arisfrom failure of neural tube closure, directly linked to folate deficiency. Hydrocephalus results from CSF flow obstruction, not NTDs, and lacks evidence for folate prevention. Both A and B overstathydrocephaluss link, while Neither ignorspina bifidas established prevention. Folatrole in neurulation targets spina bifida specifically, making B the correct answer, reflecting its unique embryologic and epidemiologic profile.

Correct Answer: B

Rationale: The posterior fontanel closat 2 months on average, per pediatric standards. Smaller than the anterior, it fusby 1-3 months postnatally as occipital suturmature. Two weeks is too early, while 12-20 months (C-E) apply to the anterior fontanel or anomalies. Early closure reflects rapid posterior skull growth cessation. Clinical observations (e.g., AAP) establish 2 months as the norm, making B the correct answer, distinct from longer anterior timelines.

Correct Answer: A

Rationale: Simple partial seizurlack loss of consciousness , per ILAE, preserving awareness during focal motor (versive, B), sensory, or autonomic events lasting 10-20 seconds without postictal confusion . Abnormal EEG is typical. Loss of consciousness defincomplex partial seizures, not simple ones. This awareness distinction, rooted in seizure classification, makes A the exception and correct answer.

Correct Answer: A

Rationale: Migraine variants include cyclic vomiting , amaurosis fugax , alternating hemiplegia , and confusional stat, per ICHD-3, tied to migraine pathophysiology. Cluster headachare a distinct trigeminal-autonomic cephalalgia, not a migraine variant, with different featur(e.g., unilateral autonomic signs). This nosologic separation makes A the exception and correct answer.

Correct Answer: A

Rationale: Sydenham chorea, post-streptococcal, featurhypotonia with milkmaids grip , choreic hand , darting tongue , and emotional lability , reflecting basal ganglia dysfunction. Hypertonia contradicts choreas flaccid, involuntary nature; rigidity suggests other conditions (e.g., dystonia). This motor distinction, per rheumatic fever literature, makes A the exception and correct answer.