High school mathematics question: Four tourist groups A, B, C, and D have 40, 10, 30, and 20 people respectively. Twenty people are selected from them using stratified sampling method...

40/(41320)=2/5

10/(41320)=1/10

30/(41320)=3/10

20/(41320)=1/5

So when stratified sampling The number of people drawn from the four tourist groups are:

Group A: 20·2/5=8 people

Group B: 20·1/10=2 people

Group C: 20·3/10=6 people

Group D: 20·1/5=4 people

And because it requires one person to browse at each location, Everyone only visits one city, and people from group B will not go to Chengdu to visit

So, it is divided into the following steps and then solved gradually according to the situation: (The numbers in the arrangement and combination are always with the larger one at the bottom and the smaller one at the top)

Select 1 person from group B: C21C31A43=144 types

Select 2 people from group B: A32C42A22=72 types

If no person from group B is selected: A44 =24 types

So, in summary, there are 240 different options. The answer is B.

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I hope the poster will adopt it! ! ! Finally, I wish the host a good study and progress!