13. The learning support method according to claim 12 , wherein: the achievement degree estimating operation includes an operation of comparing the number of types of perturbation within the questions to which the correct answer has been given, with a predetermined number-of-types threshold value, in a case where the delay time of the answer is equal to or smaller than the predetermined delay-time threshold value; and the question generating operation includes an operation of generating the word changed in accordance with the perturbation of the different type, and setting the question relating to the generated word as the candidate for the question, in a case where the number of types of perturbation within the questions to which the correct answer has been given is larger than the predetermined number of types threshold value.
13. The learning support method according to claim 12 , wherein: the achievement degree estimating operation includes an operation of comparing the number of types of perturbation within the questions to which the correct answer has been given, with a predetermined number-of-types threshold value, in a case where the delay time of the answer is equal to or smaller than the predetermined delay-time threshold value; and the question generating operation includes an operation of generating the word changed in accordance with the perturbation of the different type, and setting the question relating to the generated word as the candidate for the question, in a case where the number of types of perturbation within the questions to which the correct answer has been given is larger than the predetermined number of types threshold value. 14. The learning support method according to claim 13 , wherein: the achievement degree estimating operation includes an operation of referring to the learning history database and comparing a consecutive wrong answer count with a predetermined consecutive-wrong-answer threshold value, 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 number-of-types threshold value; and the question generating operation includes operations of: setting the question relating to the word, which is of the same type of perturbation as the question to which the correct answer has been given and has different perturbation, as the candidate for the question, in a case where the consecutive wrong answer count is larger than the predetermined consecutive-wrong-answer threshold value; and setting the same question as the question to which the answer has been input, as the candidate for the question, in a case where the consecutive wrong answer count is smaller than the predetermined consecutive-wrong-answer threshold value.