Answer:
D, Out of every 10 books total on Caleb's bookshelf, 7 are nonfiction.
Explanation:
When we are dealing with ratios it is common to hear phrases such as "for every". In this circumstance for every 10 books Caleb has on his bookshelf, 7 of them are always nonfiction. This can also be used if we want to expand the ratio, for example, 14:20. The ratio would still be equivalent to 7:10 because each factor increased at the same rate.