8. A learning support method to be performed by a learning support system, the learning support system which includes a computer including a processor and a memory including: a question database in which a question to be asked of an answerer is stored; and a learning history database in which a result of giving an answer to the question asked of the answerer, is recorded, the learning support method including: a question generating operation of generating a question relating to a word changed in accordance with perturbation that changes a word, and storing the question in the question database; a question presentation operation of asking the answerer the question extracted from the question database; an answer acquisition operation of receiving the answer to the asked question; a scoring operation of determining correctness or wrongness of the answer by referring to the question database; and an achievement degree estimating operation of storing a result of the determination, in the learning history database, wherein: the achievement degree estimating operation includes an operation of comparing 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 generating operation includes operations of generating 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 setting a question relating to the generated word as a candidate for the question.
8. A learning support method to be performed by a learning support system, the learning support system which includes a computer including a processor and a memory including: a question database in which a question to be asked of an answerer is stored; and a learning history database in which a result of giving an answer to the question asked of the answerer, is recorded, the learning support method including: a question generating operation of generating a question relating to a word changed in accordance with perturbation that changes a word, and storing the question in the question database; a question presentation operation of asking the answerer the question extracted from the question database; an answer acquisition operation of receiving the answer to the asked question; a scoring operation of determining correctness or wrongness of the answer by referring to the question database; and an achievement degree estimating operation of storing a result of the determination, in the learning history database, wherein: the achievement degree estimating operation includes an operation of comparing 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 generating operation includes operations of generating 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 setting a question relating to the generated word as a candidate for the question. 10. The learning support method according to claim 8 , wherein: the learning support system further includes a perturbation rule database that includes at least any two of the types of perturbation being a synonym, an antonym, and a modification rule; and the question generating operation includes an operation of setting the question relating to the word changed according to the perturbation of the different type, as the candidate for the question, by: selecting the word to be the question from the perturbation rule database; selecting modification of the selected word from the perturbation rule database, by a random number; and generating the question relating to the word subjected to the selected modification.