What is the primary mechanism of action of methotrexate in rheumatoid arthritis?

Correct Answer: A

Rationale: Methotrexate primarily works by suppressing the immune system, reducing inflammation in rheumatoid arthritis.

Correct Answer: D

Rationale: Truancy is not a recognized feature of ASD.

Correct Answer: B

Rationale: Amphetamine intoxication matches these symptoms, including autonomic hyperactivity, psychosis, and cardiovascular effects.

Correct Answer: C

Rationale: Congenital pneumonia with sepsis is likely given the low WBC count, prematurity, and need for ventilation

Correct Answer: C

Rationale: The anion gap is calculated as (Na⁺ - [Cl⁻ + HCO₃⁻]) and represents unmeasured anions in plasma. It helps differentiate metabolic acidosis causes, with high values suggesting lactic acidosis or toxin ingestion.