The correct answer is B.
The focus of co-locating is to help communication. Did you pick choice A because you thought having everyone in one office might save money? Not necessarily. There are many reasons that A is not always true, thus A is not the BEST choice. The same can be said for choices C and D. The schedule could be accelerated by co-location and there could be improved instances of opportunities being found of having everyone in one office, however, these would not always be true and thus they are not BEST. Only B is always true.
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