Question

mrs. weavers class read an article about how humans unintentionally damage ecosystems. the class learned that while fishing for tuna, fishermen have also killed thousands of dolphins accidentally caught in nets. based on several graphs, the students made a chart that included data over a 21 - year period.
dolphins killed
(1960 - 1980)
which is the best explanation for the drastic decrease in the number of dolphins killed after 1975?
tuna fishing was banned in 1975.
dolphins stopped swimming with tuna.
economic and political pressures were brought against tuna fishermen.
dolphin deaths and tuna catches were not considered important after 1975.

Explanation:

• Option 1: If tuna fishing was banned, the data would likely show a more immediate and extreme drop, but the problem doesn't mention a ban.
• Option 2: Dolphins' behavior change is not a common or likely reason for such a large - scale decrease in deaths.
• Option 3: Economic and political pressures (such as consumer boycotts, environmental regulations) can lead to changes in fishing practices. Fishermen might have adopted dolphin - safe fishing methods due to these pressures, which would explain the decrease in dolphin deaths.
• Option 4: If they were not considered important, the number of dolphin deaths might not decrease but rather stay the same or even increase.

Answer:

Economic and political pressures were brought against tuna fishermen.