Zoom in if u can't see but tell me the correct answer and show me the work

I think she will need 3 cups of flour. B. If 2 cups make 20. Then 2 more cups would make 40. so i think it would be 3 cups. Which is in between 2 and 4. And 30 is in between 20 and 40.  
I hope this will help you!!

We know that 2 cups of flour makes 20 biscuits.

2/2=1
20/2=10

To make 10 biscuits, you need 1 cup of flour. I know that because I cut the amount of flour in half because half of 20=10.

10 x 3 = 30

Because 10 times 3 is equal to 30, you can multiply the amount of flour by three to find out how much flour you will need for 30 biscuits.

1 x 3 = 3

You will need 3 cups of flour to make 30 biscuits.

The correct answer is B.

Hope this helped :)! Tell me if you want me to explain it in a different way.