+ Question 20 should be E as instructed

+ Question 1 cannot be A or B and question 2 cannot be B because of question
1

+ The pair 10 and 16 have answers  A and D respectively.

+ The pair 6 and 17 do not have answers A,C,E. Question 2 says that question
  16 and 17 cannot have the same answer leaving only answer B acceptable for 
  question 17 and D for 6.

+ Question 13 says that the answer A can be removed from question 3,5,7,19
  and 13 itself because than the answer C will be correct. Therefore, answer 
  C for 13 and A for 9 are not correct. We know that question 17 has answer B 
  so answer E is wrong as well.  The answer A for question 11 conflicts with 
  question 1, leaving only D as an answer to question 13.

+ Question 15 has answer A and so does question 12.

+ Question 9 and 10 cannot have the same answer and so with 10 and 11.
  Answers D,E for question 2 and not right.

+ Question 7 leaves answers A,C,E possible for question 8. The available
  answers to 3 and 4 also remove answer A.

+ Question 2 removes the answers: D for 5, E for 7, A&D for 14, B for 18 and
  E for 19.

+ The answer B is not correct for 5 and so answer E is not right for the
  first question.

+ Answer D for 5 was removed. Thus, we can remove D for question 4.

+ The sum of answers A or E is 6 or 8 (question 8). Because of question 1
  the answer to question 4 must be the remaining odd number 5 - answer B.

+ Question 3 may have answer B or D (odd number) leaving answer E for 5.

+ Questions 5 and 20 have answer E so B is not correct for 3 leaving only D.
  So the answer to question 1 is D and the answer to question 8 is E.

+ All answers E for all remaining questions are wrong.

+ Question 9 and question 8 cannot have the same answer (E) leaving answer A
  for 2 and D for 7.

+ There are 5 answers A (question 4) 3 answers E (question 3) and more than
  5 answers D (question 14) leaving only answer A suitable for 18.

+ Answer B is not correct for 9 (conflict with 11) and also C is wrong,
  leaving only D.

+ Question 1-10 are filled so the answer for 11 is B.

+ There are three questions with answer B (4,11,17), two open questions
  (14,19) and according to 18 there should be five B answers so we fill B 
  for 14 and 19.

+ A good check is to count the number of D answers which is 7 right like the
  answer to 14.

When we collect all the answers we get: DAD BEDDED A BAD BAD BABE

Now the only remaining question is who in his right mind can build such a
test? ;-)

Shoham Ziv (sziv@baan.nl)
Israel