It's a good book, but they got a little sloppy, especially towards the end. You should check out the errata
Somewhat inconveniently, there is the confirmed errata on the latest printing (some of which seem to be fixed anyway in my book), a set of unconfirmed errata (many of which are wrong, while many others are right), and changes fixed from old printings.
It seems to me you have an old printing because question 4 in my book only shows answer A as correct. For question 12, I think B and D are both correct, but I could be wrong.
Joined: Oct 31, 2005
Can you tell me the version of your book. I have August 2005 version.
Also the errata you provided for Head First Java not EJB. Can you provide the EJB link pls,
My printing is also labeled August 2005, but seems to have corrections not made to yours. After looking at the errata, I think I may see the problem you are having with 12-D on page 434. In my version, it reads: