Question

in this text, rachel m. barker discusses different types of rocks. geology is the study of rocks and other material that make up the earths surface. (1) geologists classify rocks in three groups, according to the major earth processes that formed them. the three rock groups are igneous, sedimentary, and metamorphic rocks. anyone who wishes to collect rocks should become familiar with the characteristics of these three rock groups. knowing how a geologist classifies rocks is important if you want to transform a random group of rock specimens into a true collection. igneous rocks are formed from melted rock that has cooled and solidified. when rocks are buried deep within the earth, they melt because of the high pressure and temperature the molten rock (called magma) can then flow upward or even erupt from a volcano onto the earths surface. when magma cools slowly, usually at depths of thousands of feet, crystals grow from the molten liquid, and a coarse - grained rock forms. when magma cools rapidly, usually at or near the earths surface, the crystals are extremely small, and a fine - grained rock results. a wide variety of rocks are formed due to different cooling rates and different chemical makeups of the original magma. obsidian, granite, basalt, and andesite porphyry are four of the many types of igneous rocks. question 19 how does the introduction contribute to the development of ideas in the text? (paragraph 1) a. it states how difficult it is to tell the rock types apart. b. it describes the characteristics of the three types of rocks. c. it suggests that some rocks are easier to identify than others. d. it establishes the importance of knowing the main rock types.

Explanation:

To solve this, we analyze the introduction (paragraph 1). The text says "Anyone who wishes to collect rocks should become familiar with the characteristics of these three rock groups. Knowing how a geologist classifies rocks is important if you want to transform a random group of rock specimens into a true collection." Also, it introduces the three rock groups (igneous, sedimentary, metamorphic) and starts explaining igneous rocks. Option D says it establishes the importance of knowing main rock types. The introduction emphasizes the importance of knowing rock groups (main types) for collecting and classifying, which matches D. Option A is wrong as it doesn't talk about difficulty. Option B: the introduction introduces the groups and starts explaining one, not describing all three's characteristics (that comes later). Option C: no mention of ease of identification. So D is correct.

Answer:

D. It establishes the importance of knowing the main rock types.