Apple, the Apple logo, and iBooks are trademarks of Apple Inc., registered in the U.S. and other countries. SAT® is a registered trademark of the College Entrance Examination Board, which was not involved in the production of, and does not endorse, these products. ACT® is a registered trademark of ACT, Inc. Houghton Mifflin Harcourt has no affiliation with ACT, Inc. and our products are not approved or endorsed by ACT, Inc. *AP is a registered trademark of the College Entrance Examination Board, which was not involved in the production of, and does not endorse, these products. American Heritage® is a registered trademark of American Heritage, Inc. HISTORY® and related logos are the property of A&E Television Networks (AETN). CURIOUS GEORGE, created by Margret and H.A. Rey, is copyrighted and trademarked by Houghton Mifflin Harcourt. All rights reserved. Reader Rabbit® is a registered trademark of HMH Consumer Company. Kindle® is a registered trademark of Amazon Technologies, Inc. Go Math! Academy® and the Go Math! Academy logo, CliffsNotes®, and The Learning Company® are trademarks or registered trademarks of Houghton Mifflin Harcourt.