Final answer:
Scientific and technological advances are the factors that most significantly advanced the practice of nursing in the 20th century, with major contributions from improved sanitation, behavioral changes, and crucial medical discoveries such as the development of immunizations and antibiotics.
Step-by-step explanation:
The factor that best advanced the practice of nursing in the 20th century was c) Scientific and technological advances. The 20th century saw a significant rise in life expectancy which can be attributed to three primary factors that also heavily influenced the advancement of nursing. Firstly, improved sanitation systems played a crucial role in disease prevention. Secondly, changes in public behavior, such as the importance of hygiene, contributed to health advance. And thirdly, medicine underwent revolutionary changes with the development of immunizations and the discovery of antibiotics, notably penicillin, which brought infectious diseases under control. Moreover, innovations in medical technology and the systemic approach within health services have led to standardized practices in nursing care, greatly impacting the profession's efficiency and effectiveness.