To solve this question, the user must understand the meaning of the word "except" and the logical relationship between the sentences.
The sentence means that all children are coming, except for John. In other words, John is the only child who is not coming.
Option B is correct because it accurately reflects the meaning of the sentence. The sentence explicitly states that John is not coming, so the statement "All children are coming except John" is true.
Option A is incorrect because it contradicts the information given in the sentence. The sentence clearly states that John is not coming, so it cannot be true that all children are coming.