Macbeth Act 2 questions and answers

What is the signal Lady Macbeth is supposed to give Macbeth to let him know that she has gotten the guards drunk? She is supposed to ring the bell.
What excuse does Lady Macbeth give for not killing King Duncan herself? She says that he looked like her own father sleeping.
Tell why Macbeth won’t take the daggers back to the scene of the crime. He says he’s afraid to think of what he has done or to look at it.