The plates make up Earth’s outer shell, called the lithosphere. (This includes the crust and uppermost part of the mantle.)1 Churning currents in the molten2 rocks below propel them along like a jumble of conveyor belts in disrepair. Most geologic activity stems from the interplay where the plates meet or divide. PART A: Read the sentence from paragraph 2: “Churning currents in the molten rocks below propel them along like a jumble of conveyor belts in disrepair.” How does this sentence contribute to the reader’s understanding of the topic of the article? A by describing the geologic features that can form along each of the three types of tectonic boundaries
B
by providing an analogy connecting the concept of moving tectonic plates to a concrete image
C
by signaling a shift in the structure of the article to a chronological narrative
D
by connecting the introduction of the article to the central idea that the lithosphere is unique to planet Earth