Answer:
C. Claire has 10 country CDs and 5 Jazz CDs
Explanation:
means that 10 out of 15. So we can assume that in total she has 15 CDs and 10 of them are Country and the other is Jazz.
This would rule out choice D.
If we reduce this fraction then we would have:
This means that two-thirds of her CDs are country music. So this would rule out A and B choices.
Now C is correct because 10 country plus 5 Jazz is equal to 15 CDs. So we have the correct total.
The answer is C.