Which of the following most accurately describes changes in life expectancy?
a. life expectancy was relatively low until 1750, when it increased extremely rapidly.
b. life expectancy has increased steadily during the past 6,000 years?

A24-year-old g4p2 woman at 34 weeks gestation complains of a cough and whitish sputum for the last three days. she reports that everyone in the family has been sick. she reports a high fever last night up to 102°f (38.9°c). she denies chest pain. she has a history of asthma with no previous intubations. she uses an albuterol inhaler, although she has not used it this week. vital signs are: temperature 98.6°f (37°c); respiratory rate 16/minute; pulse 94 beats/minute; blood pressure 114/78; peak expiratory flow rate 430 l/min (baseline documented in the outpatient chart = 425 l/min). on physical examination, pharyngeal mucosa is erythematous and injected. lungs are clear to auscultation. white blood cell count 8,700 mcl; arterial blood gases on room air (normal ranges in parentheses): ph 7.44 (7.36–7.44); po2 103 mm hg (> 100); pco2 26 mm hg (28–32); hco3 19 mm hg (22–26). chest x-ray is normal. what is the correct interpretation of this arterial blood gas?