The essential QAndA companion book to First Aid for the? USMLE Step 1. . First Aid? QAndA for the USMLE Step 1 features 1,000 board-style questions and answers, along with explanations for both correct and incorrect answers. The content is keyed to First Aid for the? USMLE Step 1, allowing you to study high-yield facts and QAndAs simultaneously. All questions have been reviewed by students who just aced the exam.