Estimating sample size I have $5$ different options: ($a,b,c,d,e$) out of which one is correct ($c$ in  this case).
What should be the sample size (the number of people I should ask to answer) so that I can get $80\%$ confidence that the correct answer is chosen?
Thanks

Without knowing something about the accuracy of the responses there is no answer.  If your respondents are 100% accurate, one is enough.  If they are random, no number is enough.
