The correct answer is Better than. Key Points The use of 'Best than' is inappropriate for the given sentence. 'Best' is the superlative degree of an adjective 'Good'. 'Superlative degree' is used to describe an object which is at the upper or lower limit of quality (the tallest, the smallest, the fastest, the highest). They are used in sentences where a subject is compared to a group of objects. In the given sentence, a comparison between the two aspects is given, therefore a 'Comparative degree' of 'Good' should be used. 'Comparative degree' of 'Good' is 'Better'. ​Hence, the underlined part of the sentence should be replaced by 'Better than'. ​Correct sentence: She liked him better than the other two kittens.​ ​Additional Information The 'Comparative degree' is used when you are comparing two items. Most comparatives use the ending er, like smarter, faster, and smoother. Typically, 'Than' is used with 'Comparative degree'. Example: He is faster than his sister.