Remember: The goal isn't to finish the book. The goal is to read like a National Geographic explorer. And explorers don't use cheat sheets.
The most reliable and comprehensive versions of the answer key are typically found in the or through official educational platforms. reading explorer 1 third edition answer key pdf
Since I cannot post the full 200-page key, let me give you a fair-use example of how to check your critical thinking, not just your multiple-choice answers. Remember: The goal isn't to finish the book