There are still many ways to choose when doing multiple-choice questions. Commonly used methods are: substitution method, exclusion method, graphic method, reverse reasoning method, counterexample method and so on.

Substitution method: that is, substitute a specific number for an alternative answer, and if it conflicts with the hypothetical conditions or well-known facts, it will be rejected.

Algorithm: The given condition in the stem is an analytical formula.

Graphic method: it is suitable for the case that the given function has certain characteristics in the stem, such as parity, periodicity or that the given event is two events, and it is particularly simple to do it with graphic method.

Exclusion method: exclude three, and the fourth is the correct answer. This method is suitable for the case that the given function in the stem is an abstract function.

Inverse inference: The so-called inverse inference is to assume that one of the four selected answers is correct, and then do the inverse inference. If the obtained result conflicts with the question setting condition or the well-known correct result, the alternative answer is rejected.

If you find that neither method works in the exam, you can also choose the guessing method, with at least 25% accuracy. For more knowledge points, please pay attention to Beijing New Oriental Postgraduate Mathematics Course ~