Hey there! I'm happy to help!
-------------------------------------------------------------------
<u>OVERVIEW</u>
Random sampling is when you take a sample of something completely at random. This is done to avoid bias and other stuff like that. It makes the data a lot more pure, real, and factual.
-------------------------------------------------------------------
<u>CHOOSING THE ANSWER</u>
OPTION A: A SCHOOL NEWSPAPER ASKS TEACHERS IN THAT MIDDLE SCHOOL HOW THEY FEEL ABOUT THE BEHAVIOR OF TWELVE YEAR OLD BOYS.
Does this seem very random to you? They're asking all the teachers who work at a certain junior high to talk about twelve year old boys. But, the teachers are definitely going to have some sort of bias towards twelve year old boys because they work with them, and since all of the samples are teachers, this is going to have biased data. Therefore, answer A is incorrect.
OPTION B: A NATIONAL SURVEY COMPANY PICKS ONE PHONE NUMBER FROM EACH AREA CODE IN AMERICA TO CALL AND ASK FOR AN OPINION ON CURRENT POLITICAL ISSUES.
This definitely seems a lot more random. There is only one phone number from each area code and there are many area codes in the United States so you get a bit of what everyone thinks about an issue. There is no bias because there is one random phone number and there are many different places this is done. Therefore, option B is correct.
OPTION C: MIGRANT WORKERS ARE SURVEYED ON THEIR OPINION OF MANDATORY HEALTH INSURANCE FOR COMPANIES.
This is not very random because they are asking a specific group of workers about a company and business ordeal. It is not very random because the migrant workers are specifically being asked, not random people. Therefore, option C is incorrect.
-------------------------------------------------------------------
<u>THE SOLUTION</u>
Therefore, Option B is the correct answer.
I hope that this helps! Have a wonderful day!
, where H is a height of cone and R is a radius of the bottom. 
.