单项选择题

A.PO2≤55mmHg或SO2≤88%
B.PO2≤55mmHg或SO2≤89%
C.PO2≤60mmHg或SO2≤88%
D.PO2≤60mmHg或SO2≤89%
E.PO2≤60mmHg或SO2≤90%