Passage I
Scientists categorized each of the 300 pearly mussel species native to North America. If there were sufficient data to determine a species' risk of extinction, it was placed in 1 of 5 risk categories; otherwise, it was placed in a separate category (see Table 1).
Zebra mussels (a nonnative species) are thought to damage pearly mussel populations in North America. Zebra mussels became abundant in the Hudson River estuary in late 1992. Figure 1 shows the number of native pearly mussels in the Hudson River estuary late in each year from 1992 through 2002.
2. Based on Figure 1, how many pearly mussels were most likely present in the Hudson River estuary when zebra mussels became abundant there?
Your Answer is
Correct Answer is G
Explanation
From the first sentence of the second paragraph of the article, we can see that the number of zebra mussels increased in 1992. Look at figure 1, when the abscissa is 1992, the number of pearly mussels on the ordinate is about 1000-1200 million