I'm not sure whichonesof the following are correct.
1. Dog/A dog is my favorite animal.
2. My favourite animal is dog/a dog/dogs.
3. My favorite animals are dogs.
Yes.How about "My favorite food is chips no full stop here"? Is it right?
But "is" is singular, "chips" are plural.Yes.
When a linking verb is used
A linking verb (“is,” “are,” “was,” “were,” “seem” and others) agrees with its subject, not its complement.
Joe’s favorite dessert is blueberry muffins.Blueberry muffins are Joe’s favorite dessert.
"Favourite food" is singular.But "is" is singular, "chips" are plural.
1. Then "My favorite animal is dogs" is correct?Subject-Verb agreement.
Subject-verb Agreement
Watch the subject-verb agreement in your sentences when… When the subject follows the verb When the subject follows the verb (especially in sentences beginning with the expletives “there is” or “there are”), special care is needed to determine the subject and to make certain that the verb agrees...writing.wisc.edu
There are no above sentences on the book. I mean the grammar book says "countable nouns should be modified in sentences", such as "The dog is cute. That's my dog. I have a dog. I have two dogs." We can't say "I have dog". Then why can we say "Dog is my favorite animal"?1. No, it is not correct.
2. If you insist on telling us what you think your grammar book says, give us the title and author. If it actually recommends "A dog is my favourite animal" the book is no good and you should get rid of it, because no native speaker would ever say that.