Thank you for the opportunity to help you with your question!
To do number 8, you have to find what is called "unit rate". This is found by figuring out how much oil is is leaked per hour.
For A, that would be 287000000/5 = 57400000 (note the spill was in KL)
For B, that would be 260000/8 = 32500
For C, that would be 292000/0.5 = 584000 (30 minutes is the same as 0.5 hours)
So, by far, spill A had the highest rate. So the answer to question 8 is "A".
For 9, We have to figure out what was the rate for 30 minutes. This would be 0.5 hours or 0.5 times each of the rates above. We find only answers B and D are valid (Spill C times 0.5, and Spill A times 0.5). Spill A's value is greater. So D is the correct answer for question 9.
Please let me know if you need any clarification. I'm always happy to answer your questions.