Dave's ESL Cafe's Student Discussion Forums

[welkins2139]

7.All psychiatrists are doctors. Only psychiatrists were invited to the conference. All who were invited to the conference stayed at the Hefford Hote. Therefore, only psychiatrists stayed at the Hefford Hotel.
　
　　Which one of the following statements, if added as a premise to the argument, would make the conclusion valid?

　　(A) Only those who were invited to the conference stayed at the Hefford Hotel.
　　(B) All who were invited to the conference were psychiatrists.
　　(C) All psychiatrists were invited to the conference.
　　(D) No one who was invited to the conference failed to stay at the Hefford Hotel.
　　(E) Only doctors stayed at the Hefford Hotel.

Which the above is the correct answer? and why?

Thank you

[myprofe]

(A) Only those who were invited to the conference stayed at the Hefford Hotel.
No, the hotel could have had other guests.

(B) All who were invited to the conference were psychiatrists.
True.

(C) All psychiatrists were invited to the conference.
No, a group of them was invited.

(D) No one who was invited to the conference failed to stay at the Hefford Hotel.
No, they were invited but we don't know if they all accepted the invitation.

(E) Only doctors stayed at the Hefford Hotel.
No, surely there were other guests.
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