One Method to Estimate the Appropriate Size of an Oropharyngeal

One method to estimate the appropriate size of an oropharyngeal airway is by:

A) using the length of patient's middle finger plus 1 inch.
B) measuring from the corner of the patient's mouth to the tip of the earlobe.
C) using the largest airway that will fit into the patient's mouth.
D) measuring from the middle of the patient's mouth to the tip of the earlobe.