Me head is spinning! What's a poor EFL teacher to do, you lot bunging these damn threads in here and I keep thinking,"Jesus! I'm glad I don't get these questions in my classes." And whaddaya know! That very day I get some pinickerty student come up to me and ask me. Then I come on to the 'net ( apostrophe included) and find you lot talking about it, after I have blustered my way through an explanation, that wouldn't convince an ijjit.