• Custom models that you can use for AMC lookalike audience generation
• Credentials for the S3 bucket that you have connected to your AMC instance
• Synthetic signals that exist within an AMC sandbox instance, which mimic the structure and statistical properties of those records in an advertiser instance
• Parameters that can be invoked in your SQL query and replaced by specified values during query execution

The correct answer is: Parameters that can be invoked in your SQL query and replaced by specified values during query execution

Explanation: Custom parameters in AMC are placeholders that can be defined and invoked in your SQL query and are replaced by specified values during query execution. They allow you to make your SQL queries flexible and reusable, so you don’t need to hard-code values directly into your query.

Reference content: From the official Amazon documentation (AMC SQL expressions):

“CUSTOM PARAMETER. Return input parameter value by name set at the workflow definition level.”

Additionally, the AMC workflow guide (Manage a workflow) states:

“The AMC workflows API supports the ability to create custom parameters … then allows you to pass values to these parameters at execution…”