Hi JohnParis,

Thank you so much for explaining this to me. Many (maybe all, I have to check) the exercises or tests published here provide "key" to exercises and tests, which do make us think "key" is "answer". I hope I can forget "key" as soon as possible.

I do not know you provide your email address. I shall look at it after I reply your post. And if any publishers try to argue I shall give them your email address.
I don't know what has happened to this website. "Post reply" does not show here.

Have a nice weekend.