This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
It is possible for a Business Delegate to reduce network traffic if you implement caching in the Business Delegate.
However, caching is not a primary focus of the Business Delegate pattern, so for the exam you can typically assume Transfer Object is the correct answer to any such question.
On the real exam, you also typically get a list of four or more consequences to describe a pattern, not just one. If the real exam expected an answer of Business Delegate they'll provide at least one very obvious clue.
Unfortunately, some mock exams only give you a single consequence or the questions' authors confuse the patterns. For those trying to study, such questions hurt more than help. That's why I made my patterns study document.