1. Teacher Guide This lesson is designed to teach kids to ask a critical thinking question that you can’t just put into a search box to solve. To do that, we encourage them with smaller questions that search can help them answer. Make sure that you read the notes for each slide: they not only give you teaching tips but also provide answers and hints so you can help the kids if they are having trouble. Remember, you can always send feedback to the Bing in the Classroom team at BingInTheClassroom@Microsoft.com. You can learn more about the program at bing.com/classroom and follow the daily lessons on our Partners In Learning site. BingInTheClassroom@Microsoft.combing.com/classroomPartners In Learning site Want to extend today’s lesson? Consider using Skype in the Classroom to arrange for your class to chat with another class in today’s location. And if you are using Windows 8, you can also use the Bing apps to learn more about this location and topic; the Travel and News apps in particular make great teaching tools.Skype in the Classroom This lesson is designed to teach the Common Core State Standard:

2. Main Critical Thinking Question © Carsten Peter/Getty Images

3. There are several notable caves in Phong Nha-Kẻ Bàng National Park in Vietnam. But just five years ago, the world learned of the park’s Son Doong Cave, which is now considered the largest known cave on Earth. Aside from its immense size, Son Doong contains other unique features as well, including a forest inside the cave, a rushing river, and these limestone cave pearls. Cave pearls form when fast-moving water pulls calcite from the surrounding stone, depositing it around a grain of sand. As more water flows past, the calcite layer grows and coats the sand evenly, making a spherical shape. Some cave pearls can even take on a white gloss similar to the pearls that form inside mollusks. Main Critical Thinking Question

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