When Humans Take Short Trips to Places of High Altitude

When humans take short trips to places of high altitude, their hemoglobin

A) is more saturated with O₂ than it was at lower altitudes.
B) delivers more O₂ to tissues as the level of BPG increases.
C) quickly becomes more concentrated in red blood cells than it was at lower altitudes.
D) shifts its O₂-binding/dissociation curve to the left.
E) resembles fetal hemoglobin in terms of its O₂-binding function.