In the early days of antibiotic use , penicillin and sulfonamide were used to successfully treat a variety of bacterial infections . in later years stronger antibiotics were needed because some bacteria were either resistant to or not affected by these same antibiotics . this situation is best explained ?

Which greenhouse gas is emitted when burn fossil fuels for energy? a.nitrogen b.oxygen c.carbon dioxide d.helium

What is the goal of cellular respiration

Which of the following statements best distinguishes a hypothesis from a theory? a. theories are hypotheses that have been proved. b.hypotheses are guesses; theories are correct answers c. hypotheses usually are relatively narrow in scope; theories have broad explanatory power. d. theories are proved to be true; hypotheses are often contradicted by experimental results.