I agree with Rabbie - if you want to extend it to 40, 60, 150 questions, you won't be able to keep on adding fields for the answers.
For your existing question though (and assuming these are text fields - based on the fact that they can contain 'n/a' as well as yes or no), I would handle it a bit differently - this method is a bit quick and dirty, but it should work:
Instead of checking each field for the value, concatenate all the fields together and check the resulting mess for the presence of 'No', something like:
SELECT tblAnswers.*
FROM tblAnswers
WHERE (([Q1] & [Q2] & [Q3] & [Q4] & [Q5] & [Q6] & [Q7] & [Q8] & [Q9] & [Q10] & [Q11] & [Q12] & [Q13] & [Q14] & [Q15] & [Q16] & [Q17] & [Q18] & [Q19] & [Q20]) Like "*No*");
What this basically does, is to create - on the fly, for each record - a big string that probably looks something like "YesYesYesYesNoYesYesYesNoYesYesN/aYesYesYesYesYesYesNoN/a", then checks if the string 'No' appears in it anywhere
This approach could go wrong if some chance confluence of different values happened to match the string your're looking for - i.e. if the possible answers included (silly example) 'Aye' and 'Sure' as well as Yes, No, etc, Because 'AyeSure' contains the string 'yeS' (granted it probably wouldn't make a difference in this silly example, as they are all affirmative)