This is a question I would like to have an explanation with: It's in this PDF, question 9.
In that circuit, if switch 1 is closed, bulb A burns normally. If 2 is closed as well, do other lamps burn normally as well?
The answer is D: yes, both B and C, but why? Could somebody explain the steps in order to think? This is not homework (even though in principal it is) but I did this voluntarily on my own interest in how more advanced electrical circuits work.