The infinitive verb is a verb with the word 'to' in front of it. This verb is always just a verb. There is no - ed, no - ing, no - s at the end of the verb. Thus, options A, C and D are wrong according to the rule. The correct option is B since 'to' is in front of the base verb 'be'. Hence, sentence would become: He claimed to be the best player of hockey.