The sentence that contains extraneous information and should be deleted is J Sentence 11.
The main focus of the third paragraph (sentences 8-10) is about how horses have developed a method to sleep while standing and be ready to escape from predators quickly. Sentence 11, which states that horses have bigger eyes than most other animals, does not directly contribute to the discussion about their sleeping habits and is therefore not necessary for the overall clarity or purpose of the paragraph.