Directions: Choose the word or words that best complete the sentence. 1. The __ - Is the Earth's land or crust. A hydrosphere B atmosphere C biosphere D lithosphere 2. According to the theory of __ the Earth's continents were once joined in one large landmass and then separated. A evolution B motion C continental drit D relativity 3. In the process cf __ Farth's surface is worn down by wind, glaciers, and water. A folding B plate tectonics C erosion D weathering 4. A saturated, porous underground layer of rock through which water flows slowly is __ A a spring B an aquifer C a desalinization D apool Reviewing Main Ideas Directions Choose the best answers to the following questions. Section 1 (pp. 30-23) 5. Gravity is the physical force that A creates the asteroid belt. B. is due to the sun's small mass and the lack of matter it contains. C establishes and maintains the order of the planets. D keeps the planets and other objects revolving around the sun. Section 2 (pp. 34-40) 6. The force that does most of the work of wearing dawn Earth is __ A. wind B sand C water D heat Section 3 (pa (1)-44) 7. The total amount of water in the bydrosphere generally __ A decreases B increases C stays the same 8. How are the hydrosphere, the lithosphere, and the atmo- sphere related? A All are circular regions. B They are all elements that make up the biosphere. C People have no contest over the hydresphere, the licho or the atmosphere. D All three revolve around the sun.

## Step1<br />The first question asks for the term that refers to the Earth's land or crust. The correct answer is D, the lithosphere. The lithosphere is the rigid outer layer of the Earth, which includes the crust and the uppermost part of the mantle.<br /><br />## Step2<br />The second question asks for the theory that explains the movement of Earth's continents. The correct answer is C, the theory of continental drift. This theory suggests that all the continents were once joined together in a single landmass and have since drifted apart.<br /><br />## Step3<br />The third question asks for the process that wears down Earth's surface. The correct answer is C, erosion. Erosion is the process by which soil and rock are removed from the Earth's surface by exogenetic processes such as wind or water flow, and then transported and deposited in other locations.<br /><br />## Step4<br />The fourth question asks for the term that describes a saturated, porous underground layer of rock through which water flows slowly. The correct answer is B, an aquifer. An aquifer is an underground layer of rock or sediment in which water flows or from which groundwater can be extracted.<br /><br />## Step5<br />The fifth question asks for the role of gravity in the solar system. The correct answer is D, gravity keeps the planets and other objects revolving around the sun. Gravity is the force that attracts two bodies towards each other, and in the case of the solar system, it is the force that keeps the planets in orbit around the sun.<br /><br />## Step6<br />The sixth question asks for the force that does most of the work of wearing down Earth. The correct answer is C, water. Water, in the form of rain, rivers, and oceans, erodes the Earth's surface over time.<br /><br />## Step7<br />The seventh question asks about the total amount of water in the hydrosphere. The correct answer is C, it stays the same. The total amount of water in the hydrosphere remains constant, although it can change forms (e.g., from liquid to ice).<br /><br />## Step8<br />The eighth question asks about the relationship between the hydrosphere, the lithosphere, and the atmosphere. The correct answer is B, they are all elements that make up the biosphere. The hydrosphere, lithosphere, and atmosphere are all components of the Earth system and contribute to the biosphere, which is the sum of all ecosystems on Earth.