Question

geologists classify 1 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 earth’s 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 earth’s 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 21
part b: which detail from paragraph 2 best supports the answer to part a?
a. \buried deep within the earth\
b. \can then flow upward\
c. \erupted from a volcano\
d. \a coarse - grained rock forms\

Explanation:

First, we need to know the answer to Part A (though it's not shown here, we assume Part A is about how igneous rocks form, likely related to magma cooling). Then, we analyze each option for Part B:

• Option A: "buried deep within the Earth" – this is about the condition for rocks to melt, not directly about igneous rock formation from cooling magma.
• Option B: "can then flow upward" – this is about magma movement, not the result of cooling.
• Option C: "erupted from a volcano" – this is about magma reaching the surface, not the formation of the rock's grain size from cooling speed.
• Option D: "a coarse - grained rock forms" – The paragraph says that when magma cools slowly (usually at great depths), coarse - grained rocks form. This directly relates to the process of igneous rock formation based on cooling rate, so it supports the classification (or formation) of igneous rocks.

Answer:

D. a coarse - grained rock forms.