C. A 50% oxygen saturation level of blood returning to the lungs might indicate an activity level higher than normal.
The best and most correct answer among the choices provided by the question is the third choice "call 911"
Tachycardia = Too fast. A heart rate of more than 100 beats per minute<span>(BPM) in adults is called tachycardia. What's too fast for you may depend on your age and physical condition.</span>
I hope my answer has come to your help. God bless and have a nice day ahead!
