Final answer:
The most essential qualities for drapes to maintain the sterile field are barrier protection and flexibility and flammability.
Step-by-step explanation:
When selecting drapes to create a sterile field for the patient, the most essential drape qualities are barrier protection and flexibility and flammability. Barrier protection is important to prevent pathogens from entering the sterile field, while flexibility and flammability are necessary for the drapes to be easily maneuvered and not pose a fire hazard. The other options, cost/benefit ratio and limitation of environmental impact, are not directly related to maintaining the sterile field.