A major problem in the construction of new buildings _____________
A major problem in the construction of new buildings _____________.
A. is that windows have been eliminated while air conditioning systems have not been perfected.
B. is they have eliminated windows and still don’t have good air conditioning.
C. is because windows are eliminated but air conditioners don’t work.
D. is depend on the fact that while they have eliminated windows, they are not capable to produce efficient air conditioning systems.