Caution:
Any null values returned by subquery or expression that are compared to test_expression using IN or NOT IN return UNKNOWN. Using null values in together with IN or NOT IN can produce unexpected results
This is not in the local BOL of my work environment. And I have no control over that.
I used to try to answer QOTD based on my knowledge and research in BOL.
But questions like this are the reason I now run the code first and that takes the fun out of it.