How should I answer an ethics question so difficult that I can't work out the right thing to do?

What's important to remember is that when it comes to ethics, there is no 'right answer' to a complicated question. All that matters is that you come up with an answer, one that can be ethically justified. If you've managed to narrow it down to two or three seemingly equally ethical courses of action, then all of them are probably right. All you need to do then is work out if any of them is easier to justify - if one is, then that's the one you want to choose, and if nothing jumps out at you then any one of those answers will do! At the end of the day, if you're being asked an ethics question without a single apparent best answer then what they're really looking for, above anything else, is how you justify the answer you choose. If you can justify it according to the four principles of beneficience, nonmaleficience, justice and autonomy, then any answer you come up with is a right answer.