Final answer:
Options a and c are examples of negative feedback loops. Option b is not an example of a negative feedback loop. Option d does not represent a negative feedback loop.
Step-by-step explanation:
Exponential population growth (option b) is not an example of a negative feedback loop. In a negative feedback loop, a change in a system causes a response that opposes the change, leading to stability or equilibrium. One example of a negative feedback loop is environmental resistance and population growth (option a). As the population of a species increases, resources become limited, leading to increased competition and decreased reproductive success, which ultimately limits population growth. Another example is a drought leading to changes in the water cycle that cause more drought (option c). When there is a drought, plants may die which reduces transpiration, leading to less moisture in the air and less rainfall, perpetuating the drought condition. Poverty and population growth (option d) does not represent a negative feedback loop as there is no direct relationship where population growth limits poverty or vice versa.