A typical survey refers to a survey method that only collects information on typical units. A typical unit refers to a unit that has outstanding characteristics in the phenomenon being analyzed and researched. It can be an unit with extreme signs; it can also be the most common unit, which is the representative of ordinary units The general situation and characteristics of overall development can be studied through typical surveys. Of the following options, which of the following is a typical survey? ['In the survey of the summary of work performance experience of a unit, the employees who consciously select the first and last sales performance for the survey.', 'In the monthly living expenses expenditure survey of school students in a school, randomly selected. I00 school students conducted a questionnaire survey.', 'In the survey of industrial production of a city, select a few large enterprises with good business performance and enterprise profits accounting for a large proportion of all industrial enterprises.', 'In the survey of industrial production equipment in a city, investigate each production equipment of all industrial enterprises.']