Put each of the following disjunctive syllogisms into standard form, identify the disjuncts and any implicit elements, and determine whether the syllogism is valid.
A. Either I’m hearing things or someone is out in the hall singing "Jingle Bells." I know I’m not hearing things. So there’s someone out there singing.
B. Either the circuit is broken or the light bulb is dead. But I know the bulb isn’t dead, so the circuit must be broken.
C. I have to get the book here in town or else in New York next weekend. But I can’t get it here; therefore I will have to get it in New York.
D. There are only two possible responses to this threat: We send in the troops or we negotiate. Negotiation is out of the question, so we must send in the troops.
E. I can’t both go to the movies with you tonight and study for the exam, and I have to study for the exam. So I can’t go.