DDC preparation tests require an Activation Key. Each Activation Key is a unique alpha-numeric code that enables a test to be taken one “complete” time. A “complete” time is defined as each question on the test being answered correctly. Questions that are not answered correctly can be retaken until the correct answer is given. For example: If a test contains 50 questions and 45 of the questions are answered correctly, the five questions that were answered incorrectly can be answered again. Once a question is answered correctly it is considered “complete” and cannot be answered again.