17. The commision has directed advertisers to restrict the use of the word "natural" to foods that do not contain color or flavor additives, chemical preservatives, or nothing that has been synthesized.
Using your example, the answer becomes very clear. Divide the sentence to x and y, where x is "the commision has directed advertisers to restrict the use of the word "natural" to " and y is "foods that do not contain color or flavor additives, chemical preservatives, or nothing that has been synthesized" Replacing the underline portion with "or anything that has been" , the senctence can be read as follwed:
"The commision has directed advertisers to restrict the use of the word "natural" to foods that do not contain color or flaver additives, (and) chemical preservates"
"The commision has directed advertisers to restrict the use of the word "natural" to anything that has been synthesized"
Answer is d.