Watch Sal work through a basic pronoun clarity question from the SAT Writing and Language Test. Watch the next lesson: https://www.khanacademy.org/test-prep/sat/sat-reading-writing-practice/new-sat-writing-grammar/v/pronoun-clarity-harder Missed the previous lesson? https://www.khanacademy.org/test-prep/sat/sat-reading-writing-practice/new-sat-writing-grammar/v/pronoun-number-basic ... https://www.youtube.com/watch?v=VRNDGeq_hlE Note: All Khan Academy content is available for free at (www.khanacademy.org)

Choosing an indicator for a titration. From 2015 AP Chemistry free response 3c. Watch the next lesson: https://www.khanacademy.org/science/chemistry/acid-base-equilibrium/titrations/v/2015-ap-chemistry-free-response-3d?utm_source=YT&utm_medium=Desc&utm_campaign=chemistry Missed the previous lesson? https://www.khanacademy.org/science/chemistry/acid-base-equilibrium/titrations/v/2015-ap-chemistry-free-response-3b?utm_source=YT&utm_medium=Desc&utm_campaign=chemistry Chemistry on Khan Academy: Did you know that everything is made out of chemicals? Chemistry is the study of matter: its composition, properties, and reactivity. This material roughly covers a first-year high school or college course, and a good understanding of algebra is helpful. About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content. ... https://www.youtube.com/watch?v=N8bTEEgskss Note: All Khan Academy content is available for free at (www.khanacademy.org)

Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes. Khan Academy is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We offer quizzes, questions, instructional videos, and articles on a range of academic subjects, including math, biology, chemistry, physics, history, economics, finance, grammar, preschool learning, and more. We provide teachers with tools and data so they can help their students develop the skills, habits, and mindsets for success in school and beyond. Khan Academy has been translated into dozens of languages, and 15 million people around the globe learn on Khan Academy every month. As a 501(c)(3) nonprofit organization, we would love your help! Donate or volunteer today! Donate here: https://www.khanacademy.org/donate Volunteer here: https://www.khanacademy.org/contribute Credits: "Medium ground finch Santa Cruz" by putneymark (CC BY-SA 2.0), via Flickr: https://www.flickr.com/photos/putneymark/1351694843/in/photolist-RhKZd-RhL49-RhKUE-RhL8E-RhKDy-RhKRy-Rj1KP-34wMSC-34wNi1-2SjC1t-2SoQZ3-34rMMv-349SeW-2SjBGe-2SjACe-2SjzEV-2Sp1km-34sfui-3457Kx https://creativecommons.org/licenses/by-sa/2.0/ Data from Figure 5 in: Rosemary B. Grant and Peter R. Grant. What Darwin's Finches Can Teach Us about the Evolutionary Origin and Regulation of Biodiversity. BioScience. 2003. 53: 965-975. http://bioscience.oxfordjournals.org/content/53/10/965.full.pdf+html ... https://www.youtube.com/watch?v=0G2uDKYBX-c Note: All Khan Academy content is available for free at (www.khanacademy.org)

Example of using u-substitution to evaluate a definite integral More free lessons at: http://www.khanacademy.org/video?v=7hCsQOKOYS8 ... https://www.youtube.com/watch?v=7hCsQOKOYS8 Note: All Khan Academy content is available for free at (www.khanacademy.org)