Betty has grandchildren: jeni, sarah, rachel, kristen, lindsey, and carolyn. jeni, sarah, and rachel are sisters; kristen and carolyn are sisters; and lindsey is an only child. if the sisters must sit together, how many different ways can the grandchildren be seated at a circular table?

The first option is correct.

Step-by-step explanation:

We have been told that a chef knows that ground beef used for hamburger is safe to eat once it reaches 160 degrees Fahrenheit. For optimized taste and safety, he will not allow a hamburger cooked to a temperature under 160 degrees or over 170 degrees to be served.

Let us see our graphs one by one.

Upon looking at first graph we can see it shows that hamburger should be cooked under 160 degrees and over 170 degrees. It is the case which chef will not allow. So this is our graph that represents the conditions under which the chef will not allow the hamburger to be served.

Second graph represents that hamburger should be cooked at and under 160 degrees and at and over 170 degrees. This can't be our choice as it includes 160 and 170 degrees.

Third graph represents the temperature at which chef will allow hamburgers to be served that is temperature between 160 to 170 degrees Fahrenheit including 160 and 170 degrees Fahrenheit. So this can't be our choice either.

Fourth graph represents the temperature between 160 to 170 degrees Fahrenheit excluding 160 and 170 degrees Fahrenheit.

Therefore, option 1 is the correct choice.