Multi-choice problem: Continue writing the next sentence in this paragraph:

How to be green at home
Insulate your home.
Nearly half of your home's energy expenditures come from heating and cooling. To reduce the amount of heating and cooling needed, it is important for your home to be well-insulated.

A. This includes the following basics : Keep windows and doors at least half-shell. This will keep the sun in at all times.. B. In some cases, this may mean replacing the heating tower for external heating and air conditioning. The best insulation will be insulation sheets that protect your home from the sun, and not local materials like concrete.. C. This can be done by trimming back the number of windows in your home and installing insulated outdoor flooring at local construction lots. Walls and exterior structures do not need to be insulated to block out heat from outside.. D. Ideally your home would be well-insulated when it was built, but this is not always the case. To improve your home's insulation, hang thermal curtains over your windows..
D.