Take another look at the item:

If his friends walked into the bookstore (A) Boris had a stack of car magazines as camouflage, (B) but he was really reading Better Homes and Gardens, studying decorating ideas (C) to spruce up his first apartment.

You wanted to do this:

If his friends walked into the bookstore Boris had a stack of car magazines as camouflage, but he was really reading Better Homes and Gardens, studying decorating ideas, to spruce up his first apartment.

Adding a comma after ideas creates a problem. To spruce up his first apartment is an infinitive phrase. When a phrase of this type concludes a sentence, you do not need a comma to attach it.

You might want to review the rules.

Go back to the sentence to try again.

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