5. In several cities, the government is going ahead with ambitious construction projects despite the high office vacancy rates in those cities. The vacant offices, though available for leasing, unfortunately do not meet the requirements for the facilities needed, such as court houses and laboratories. The government, therefore, is not guilty of any fiscal wastefulness.

Which of the following is an assumption on which the argument above depends?

(A) Adaptation of vacant office space to meet the government’s requirements, if possible, would not make leasing such office space a more cost-effective alternative to new construction.

(B) The government prefers leasing facilities to owning them in cases where the two alternatives are equally cost-effective.

(C) If facilities available for leasing come very close to meeting the government’s requirements for facilities the government needs, the government can relax its own requirements slightly and consider those facilities in compliance.

(D) The government’s construction projects would not on being completed, add to the stock of facilities available for leasing in the cities concerned.（A）

(E) Before embarking on any major construction project, the government is required by law to establish beyond any reasonable doubt that there are no alternatives that are most cost-effective.

答案是a这题我看不太懂意思,我只知道b可以排除,有人可以帮我解释一下吗