Which non-Unicode letter characters may be used as the first character of an identifier?

The non-Unicode letter characters $ and _ may appear as the first character of an identifier.

In Java, the first character of an identifier must be a letter, an underscore (_), or a dollar sign ($). The subsequent characters can be letters, digits, underscores, or dollar signs. However, it’s important to note that Java identifiers are case-sensitive.

So, the correct answer to your question is: Unicode letter characters, underscore (_), or dollar sign ($) can be used as the first character of an identifier in Java.