1. A learning support system which includes a computer including a processor and a memory, comprising: a question database in which a question to be asked of an answerer is stored; a learning history database in which a result of giving an answer to the question asked of the answerer, is recorded; a question generator for generating a question relating to a word changed in accordance with perturbation that changes a word, and stores the question in the question database; a question presentation module for asking the answerer the question extracted from the question database; an answer acquisition module for receiving the answer to the asked question; a scoring module for determining correctness or wrongness of the answer, by referring to the question database; and an achievement degree estimator for storing a result of the determination in the learning history database, wherein: the achievement degree estimator compares a number of types of perturbation within the questions to which a correct answer has been given with a predetermined learning threshold value; and the question generator generates a word changed in accordance with the perturbation of a different type in a case where the number of types of perturbation within the questions to which the correct answer has been given is smaller than the predetermined learning threshold value, and sets a question relating to the generated word as a candidate for the question.