In the application-test for the translation college (which I am to submit within a week) they gave us particularly insidious sentences to see if we could figure them out. In most of them the "catch" was a no-brainer, but a few sentences did manage to get the better of me. Here they are:

1. It may be used in the hardness testing of plastics with pratically no change. (I'm not sure I see the catch here)
2. He took a car from the pool. ("pool" as in "storage", right?)
3. She crossed the green. (what does it mean? is it an idiom? should I just translate it as it sounds?)
4. The Federal Bank surprised Wall Street big time. (where's the catch here?)
5. Empty vessels make the most sound. (I know it's an idiom, what does it mean? I didn't manage to google an answer for that).

Would appreciate any help.