Yep, thought that was the answer too.

Question asked:

"If you enable transparent database encryption in your database, when is THE PAGE encrypted?" (Emphasis added)

So, lead me to believe the question was referring to a dirty page, as opposed to the intent of the reference cited for the correct answer:

"The server starts a background thread (called the encryption scan or scan) that scans all database files and encrypts them (or decrypts them if you are disabling TDE). "

Imagine the difference in the number of wrong answers if the question was more in line with the reference used:

"If you enable transparent database encryption in your database, when is THE DATABASE encrypted?" (Emphasis added)

While I appreciate the poster's efforts, I can't applaud this as a great question.

Here's a thought, how about a small (10 or less) person question review panel to spot problems with questions BEFORE they are posted. That would be a check on the ever-present problem with these questions?