<prompt> Which of the following is true about ventilation and perfusion in alveoli in an erect postureVentilationperfusion ratio is maximum at apexVentilationperfusion ratio is maximum at baseVentilation is maximum at apexPerfusion is maximum at apex  <response>: Apical alveoli have low ventilation and perfusion per unit volume of the lung, whereas the basal alveoli have high ventilation and perfusion.Ventilation-perfusion ratio and the PaO2 is maximum at the apex. PCO2 is maximum at the base. 