Passage V
Rock types can often be differentiated by the rare earth elements (REEs) they contain. Table 1 shows the average concentration of 2 REEs, neodymium and samarium, in 4 igneous rock types (oceanic basalt, continental basalt, andesite, and granite) and also in 3 sedimentary rock types (shale, sandstone, and dolomite).
Figure 1 shows the relative concentration of REEs in various igneous rock types and in sedimentary rocks taken as a group. Relative concentration is calculated using the following formula:
relative concentration of REE in rock type = 
Meteorites, taken as a group, are used to calculate the relative concentration because their composition is distinctly different from any Earth rock.
Figure adapted from S. Ross Taylor and Scott McLennan, “The Evolution of Continental Crust.” ©1996 by Scientific American, Inc.
26. Based on Figure 1, the relative concentration of terbium for limestone, another rock type, would most likely be:
Your Answer is
Correct Answer is H
Explanation
General knowledge questions.
Looking at table 1 and figure 1, limestone is not mentioned anywhere. But limestone is a kind of sedimentary rock, so go to figure 1 to find the line segment of sedimentary rock. The abscissa corresponding to Terbium is about 15-20