To strengthen, close the argument's one gap. The owner reasons that opening earlier will raise weekday morning sales because hundreds of office workers will soon arrive nearby in the early morning. That depends on a single unstated link: those arriving workers will actually buy from the bakery.
(A) confirms exactly that. If most of the new workers regularly buy breakfast on their way to work, then a bakery one block away that is open when they arrive is well positioned to capture those purchases, connecting the earlier hours to additional morning sales.
(B) compares weekend revenue to weekday revenue, but the conclusion is specifically about weekday morning sales. The word 'sales' makes it look relevant, but the scope does not match. (C) describes a competitor several blocks away in the opposite direction from the office, which does not bear on whether Hartwell's captures the arriving workers. (D) merely restates that the building will house several hundred workers, a fact the stem already gives, and never establishes that they will buy anything. (E) touts a quality award, which sounds favorable but says nothing about the early-opening plan or the workers' buying habits.
Only (A) supplies the missing link, so the answer is A.