A. the selected sample must be large enough. B. the selected samples shall be generally representative.

C. the selected samples can be selected according to your own preferences. Just increasing the number of investigators may not necessarily improve the quality of the survey.

Answer c

Among the following surveys, the one suitable for census is ().

A. ratings of news broadcast TV programs

B. The number of primary and middle school students in China who like math classes.

C. Service life of a batch of light bulbs

D. the weight of class one students

Answer d

The hotel has 100 identical rooms. After running for a period of time, it is found that there is a relationship between room pricing and room occupancy rate as shown in the following table. According to this relationship, in order to maximize the income of rooms, the price of each room should be ().

House price (RMB)

Occupancy rate

300 yuan 280 yuan 260 yuan 220 yuan

Answer c