Ans. (D). new antibiotic-resistant populations of bacteria.
Antibiotics cab be defined as antimicrobial substances that kill or prevent growth of bacteria and are used for treating bacterial infections. Overuse of these antibiotics has led to potentially serious health effects, such as development of antibiotic-resistant bacteria.
These bacteria are known as super bugs or multidrug-resistant bacteria as they have developed resistance for multiple antibiotics and cause serious infections that cannot be treated with common antibiotics.
Thus, the correct answer is option (D).