Wow, what a bunch of cynics?!?!
Option A, but be guarded so that if they aren't trust worthy you don't get burned. Jerks will be jerks, but even reasonably good folks can be tempted, so don't bait them. Just trust folks to be reasonably honest.
My Dad used to keep a regular loop and hasp lock on his pick-up truck bed with a pad lock. Knowing how poorly attached the thing was to the truck and how easy it was to break a window to get in or something I asked him why it was there. His answer..."to keep honest people honest". If someone really wanted to get in that truck, they would have, no problem. But the simple locking mechanism kept casual "peepers" from peeping into the truck bed. I like that line...."to keep honest people honest." But Dad, if they are opening up your truck they aren't honest? Leaving my truck open is baiting them, I am just keeping the casual guys out.
Its like locking your front door, that won't stop someone that really wants to get in, but it does keep out the casual guy walking past. You don't hang a sign on your front door..."house is unlocked, I am away on vacation for the week--valuable stuff is upstairs, 3rd door on the right", but I do trust that the average person isn't going to go into my home if I leave the door unlocked while I run to the corner store for a gallon of milk.
Trust people, but do so in a way as to be sure you aren't in a position to get roasted.