Answer: An author's message.
Explanation: A theme is something that an author tries to convey to the reader. Hope this helps :)
I believe that the choice we have is between "inform", "persuade", "entertain", etc: and I would say that here the purpose is to persuade. It's not an objective sentence only giving information, rather it tries to persuade people to choose this product over another one.
The first sentence, ‘My cat’s favorite pastime seems to be sleeping’.
A gerund is when a vets is used as a noun.
Future tip: gerunds most always end in ‘ing’.
Hope this helps.