Is main a valid Java identifier?

Question

One of my kids is taking Java in high school and had this on one of his tests:

Which of the following is a valid identifier in Java?

a. 123

Answer 1

main is perfectly valid because it, from the docs:

1. Is a "sequence of Java letters and Java digits, the first of which is a Java letter"
2. Is not a keyword
3. Is not a boolean literal i.e. "true" or "false"
4. Is not null literal