Which Is Correct About Energy Use in Buildings

Which is correct about energy use in buildings?

A) Future retrofitting of energy-saving systems can easily reduce an existing building's consumption to 25% of its design energy use
B) Designers cannot predict future energy use of a building
C) Retrofitting low energy systems into existing buildings is easily done in later years
D) Energy modelling predicts design energy use by a building
E) The best that future retrofitting can hope to achieve is a 25% reduction in a building's actual energy consumption