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.
1. According to Table 1, what percent of the pearly mussel species native to North America could not be placed in a category based on their risk of extinction?
Your Answer is
Correct Answer is B
Explanation
Looking at table 1, it can be found that 4% of the species have insufficient data, which cannot be included in any risk category due to insufficient data, so B should be selected