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.
3. Based on Table 1, what percent of the pearly mussel species native to North America were the scientists able to place in a risk category but did not classify as extinct or stable?
Your Answer is
Correct Answer is D
Explanation
Looking at table 1, the three groups of data that are not extinct or stable and belong to risk category should be endangered, special concern, and threatened, so the total ratio should be 26%+24%+15%=65%