(2013?Xuzhou) In the autumn and winter of recent years, "haze" weather (pictured) has frequently hit northern cities. We consider the diameter in the atmosphere to be less than or equal to 2

(1) The purpose of this experiment is to explore whether the concentration of PM2.5 in the air is related to the traffic flow. The traffic flow is different in different periods. Therefore, the variable in this experiment is the traffic flow.

(2) From the statistical results in the above table, it can be seen that the concentration of PM2.5 in the air is the largest during off-duty hours.

(3) Taking the average value of the data can reduce the experimental error. It can be seen from the data in the table that during the early morning period, the traffic flow is the least, and the average value of PM2.5 is 20.33; during the working hours, the traffic flow is the largest, The average value of PM2.5 is 86; during the noon period, when the traffic volume is small, the average value of PM2.5 is 40.67; during the off-duty period, when the traffic volume is the largest, the average value of PM2.5 is 90, which can be expressed in the form of a bar chart as follows: < /p>

(4) Analysis of data shows that PM2.5 mainly harms the human respiratory system. When air enters the lungs, it has to pass through the nasal cavity, pharynx, larynx, trachea and bronchi. PM2.5 particles are tiny and are not easily blocked by the nose and other organs. They can directly enter the bronchi and alveoli, affecting the gas exchange in the lungs and causing respiratory diseases such as asthma. disease.

(5) According to experimental conclusions, air quality can be improved by driving less, treating exhaust gases emitted by factories, and planting more trees.

So the answer is: (1) Traffic flow; (2) Maximum in the second half of the period; (3) By processing the data, it can be expressed in the form of a histogram as follows:

(4 ) Respiratory system; (5) Treat waste gases emitted by factories and plant more trees...