Sentence 3 stands out as it diverges from the main topic explored in the other sentences. While the rest of the sentences delve into the naming conventions of numbers in English, particularly highlighting the irregularities and variations within the system, sentence 3 shifts the focus to children's learning process and their comprehension of distinctions between numbers such as "fourteen" and "forty." The remaining sentences all contribute to the discourse on the complexities of English number naming, rendering sentence 3 somewhat disconnected from the central theme of the paragraph.
So, the correct option is (C): It can take children a while to learn all these words, and understand that "fourteen" is different from "forty".