For (1) I should look in the "aviation mechanics handbook", or some similar databook.
(2) Think about it this way. Start your bending moment diagram at the tip. Moving a nothingth of an inch towards the root, there's no force applying, over no distance, so there's no bending moment.
(3) Looking at what this means. Is it possible to machine (say) 1/16" thick wing skins? - of course not - so that's (a) out. Does machined mean that there's no sharp edges in the structure? - nope, so that's (b) out. Does a machined structure have a joint between two flat plates that can trap moisture? - nope, so the answer must be (c)
(4) If the stress can bend a beam (rather than compress, extent or twist it) surely there's only one direction it can be acting. If this isn't clear, take a plastic ruler, hold it down on one end against the top of the desk, and with your other hand hand it. Which way are you applying the stress?
(5) I think there are a few words missing here, I'm not sure I can see what the question is.
G