If it's on a sheet from your class-- its likely what your instructor would like you to know. It's not about what the NR prefers-- the test has no volition, sorry.
We could have an intellectual discussion about the appropriateness of various oxygen delivery devices and rates of flow, you could ask your instructor, or you could consult your friendly textbook, upon which the National Registry Exam was most likely based.
Ultimately, in the field, your method of oxygen delivery is going to be based on your assessment and impression of your patient, their symptoms and the individual circumstances. Per a textbook, every patient complaining of Chest Pain must receive O2 via NRB @ 15lpm, but as we know, that should not be the case in the field.
For a good intellectual discussion of the merits of various oxygen delivery methods in this case, check out the discussion below. Some very wise people comment. http://www.emtlife.com/showthread.php?t=12262
Hope this helps, and in due time, you find out what the National Registry "Prefers"
