Answer:
Yes, they are.
Step-by-step explanation:
The question is asked in the plural form, using "are". It may be confusing at first because the nouns "cereal", "butter", "jam" and "bread" are uncountable. However, they are all being used as the subject, which means the subject is plural. Thus, the correct answer is "Yes, they are."
Let's form another similar question as an example:
- Are coffee and water free?
- Yes, they are.
Again, "coffee" and "water" are uncountable nouns. But we still use a plural noun because they are both the subject in the sentence.