请教一个问题 june 2001 sec 4

campari

下面这个问题，第四题答案是a，请做对的童鞋点拨一下……不胜感激……


Each of exactly six doctors—Juarez, Kudrow, Longtree, Nance, Onawa,
and Palermo—is at exactly one of two clinics: Souderton or
Randsborough. The ffollowing conditions must be satisfied:

• Kudrow is at Randsborough if Juarez is at Souderton.
• Onawa is at Souderton if Juarez is at Randsborough.
• If Longtree is at Souderton, then both Nance and Palermo are at Randsborough.
• If Nance is at Randsborough, then so is Onawa.
• If Palermo is at Randsborough, then both Kudrow and Onawa are at Souderton.

1: Which one of the following could be a complete and accurate list of the doctors thatt are at Souderton?

a) Jaurez, Kudrow, Onawa

b) Juarez, Nance, Onawa, Palermo

c) Kudrow, Longtree, Onawa

d) Nance, Onawa

e) Nance, Palermo

2: If Palermo is at Randsborough, then which one of the following must be true?

a) Juarez is at Randsborough.

b) Kudrow is at Randsborough.

c) Longtree is at Souderton.

d) Nance is at Randsborough.

e) Onawa is at Randsborough.

3: What is the minimum number of doctors that could be at Souderton?

a) zero

b) one

c) two

d) three

e) four

4: If Nance and Onawa are at different clinics, which one of the following must be true?

a) Juarez is at Souderton

b) Kudrow is at Souderton.

c) Palermo is at Randsborough

d) Four doctors are at Randsborough

5: If Kudrow is at Souderton, then which one of the following must be true?

a) Juarez is at Souderton

b) Nance is at Souderton

c) Onawa is at Randsborough

d) Palermo is at Souderton

e) Palermo is at Randsborough

elleanor

Fourth rule: If Nance is at Randsborough, then so is Onawa (same clinic);

So, if N and O are at different clinics, N must at S; O must be at R.
    

Second rule: Onawa is at Souderton if Juarez is at Randsborough (J at R --> O at S; or  O at R--> J at S).

Therefore, since we have established that O must be at R, J must be at S.

That is answer A.

campari

thanx~