Final answer:
The original claim that 20% of adults smoke is symbolically expressed as 's = 20%' or 's = 0.20', where 's' represents the proportion of adult smokers.
Step-by-step explanation:
To express the original claim that 20% of adults smoke in symbolic form, the correct option is b) s = 20%. This is assuming that the variable 's' stands for the proportion of adults who smoke. Whenever we are describing percentages or proportions in a population with a variable in statistics, we write it as the variable being equal to the percentage as a decimal. Hence, 20% is expressed as 0.20, and symbolically, if 's' represents the smoking rate, then s = 0.20 would be the claim.