Short Answer 
The essential step for handling secure standardized test materials is signing a Security Agreement, which ensures commitment to maintaining the integrity of the tests. Other suggested practices, such as showing ID or limiting deliveries, are not mandatory. Therefore, the correct response is to have signed a Security Agreement.
Step 1: Understand the Importance of Security Agreements
When dealing with secure standardized test materials, the primary step is to sign a Security Agreement. This agreement signifies that the individual handling the materials understands the sensitive nature of these tests and is committed to maintaining their integrity. It outlines the necessary procedures and rules to prevent any unauthorized access or tampering.
Step 2: Overview of Alternative Options
While there are additional practices associated with test material handling, they are not mandatory. For example, alerting a colleague to witness the signing of the agreement may enhance transparency, but it is not a requirement. Similarly, verifying identity through showing ID can be useful but is not explicitly stated as necessary unless indicated in specific guidelines. Lastly, limiting deliveries to after school hours may not be practical.
Step 3: Conclude with Correct Response Identification
Based on the options provided, only the act of signing a Security Agreement stands out as essential for securing test materials. The other options (alerting a colleague, showing ID, and accepting deliveries only after hours) are not mandatory practices. Therefore, it is clear that the correct answer to the question is option B: “Have signed a Security Agreement.”