True statement regarding Pulmonary ventilation is

A i.e. PaO2 is maximum at apexVentilation perfusion ratio is maximum at the Apex of lungQ and minimum at base.In an upright positionVentilation per unit lung volume is greatest at basePerfusion per unit lung volume is greatest at base- a 2 is maximum at apex.High V- p ratio at the apex accounts for predilection of the tuberculosis for this area.In patient with unilateral lung disease the patient is positioned such that the good lung is in dependent position. Aerial oxygenation is improved in this position due to effect of gravity on ventilation.(The situation in infants is opposite. i.e. infants do better with the diseased lung in the dependent position)