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.

4. Assume that zebra mussels do damage pearly mussel species native to North America. Based on Figure 1, if all the zebra mussels in the Hudson River estuary had been removed in 2002, the population of native pearly mussels in the estuary in 2005 most likely would have been:

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

Because the question stem says that zebra mussels will destroy pearly mussels, if zebra mussels were removed in 2002, the number of pearly mussels should increase. Corresponding to figure 1, in 2002, the number of pearly mussels is about 225 million, without zebra mussels, the number should be greater than 225 million