Answer:
Strawberries : Watermelon.
Explanation:
When we look at the information given, we see that she puts 6 cups of strawberries and 18 cups of watermelon. If we arrange this into a ratio, we get:
6:18
This can also be simplified to:
1:3.
This satisfies the problem which is asking for which fruits contain a ratio of 1 to 3.