Good question, got tripped up on:
"All nonclustered indexes include the clustered index columns in their index pages"
I thought this was not true for the mere point that a table does not have to have a clustered index - meaning that some nonclustered indexes only have the RID, therefore not ALL nonclustered indexes include clustered index columns...
Good intentions with the question, but the one check box was a crap shoot (which I guessed wrong on). Better wording could have been "When a table has a unique
clustered index all nonclustered indexes include exactly
the clustered index key in their index pages." (Notice the reduction in ambiguity.)
I choose false because not all nonclustered indexes include the clustered index columns in their index pages. IE Heaps, nonclustered indexes will include a pointer to the row.
If the table is a heap, which means it does not have a clustered index, the row locator is a pointer to the row. The pointer is built from the file identifier (ID), page number, and number of the row on the page. The whole pointer is known as a Row ID (RID).