Since the beginning of this year, the persistent smog weather in China has made environmental protection and health issues the focus. In order to investigate students' knowledge of smog weather,

( 1)400; 15%; 35%; (2) 126 ; (3) See the analysis for the complete chart.

Test analysis: (1) Divide the number of students in A by the percentage to calculate the total number of students surveyed; By dividing the number of students in B by the total number of students surveyed, M can be calculated, and then N is equal to1according to the percentage sum of each part;

(2) Multiply the percentage of d by 360 to get a solution;

(3) Find out the number of students in D, and then complete the statistical chart.

Problem analysis: (1)20÷5%=400,

,

1-5%- 15%-45%=35%,

So the answer is: 400; 15%; 35%;

(2)360 ×35%= 126 ;

(3) The number of people in Grade D is 400×35%= 140,

∴ Complete the bar chart as shown in the figure.

Test site: 1. Bar chart; 2. Fan map.