The arithmetic mean describes the average trend of a set of data and is the quotient of the sum of all data divided by the number of data. When using it in statistics, it should be noted that when extreme values, vague data or heterogeneous data appear, the arithmetic mean cannot be calculated. According to the above definition, the following are suitable for calculating the arithmetic mean? ['A community counts the average age of residents in the community, including 204 children under 10 years old and 26 elderly people over 90 years old.', 'A company counts the average annual income of young employees under the age of 35, and finds that it is basically between 100,000 and 120,000 yuan. One of them is a company executive and the annual income is more than one million yuan.', 'A school counts the average height of young people in the school, and counts all the students in the preschool, primary school and secondary school of the school.', 'A city counts the average number of left-behind children in various districts and counties of the city. Among the districts and counties with a large number of migrant workers, accurate statistics are not available, and only the estimated data are provided.']