Base your answer to the following question on the information below and on your knowledge of biology. After the Aswan High Dam was built on the Nile River, the rate of parasitic blood-fluke infection doubled in the human population near the dam. As a result of building the dam, the flow of the Nile changed. This changed the habitat, which resulted in an increase in its population of a certain aquatic snail. The snails, which were infected, released larvae of the fluke. These larvae then infected humans. This situation best illustrates that (1) the influence of humans on a natural system is always negative in the long term (2) the influence of humans on a natural system can have unpredictable negative impacts (3) human alteration of an ecosystem does not need to be studied to avoid ecological disaster (4) human alteration of an ecosystem will cause pollution and loss of finite resources

According to the text, parasitic blood-fluke infection increased after the construction of the Aswan High Dam. Thus, the flow of the river changed, affecting the habitat of the aquatic snail that produces the larvae. As a result, the impact of humans can have negative consequences in the environment.

The rest of the options are incorrect because the text does not suggest that human influence is always negative, nor that it causes pollution or loss of finite resources. Finally, the paragraph does not mention either that human alterations should not be studied.