The correct answer is D. Extension cords.
Extension cords are not an acceptable method of distributing small power outlets throughout an open plan office area because they are a tripping hazard and can cause electrical fires. They are also not as reliable as other methods, such as power poles, power skirting, and flush floor ducting.
Power poles are vertical poles that are installed in the floor and have power outlets on them. They are a safe and reliable way to distribute power in an open plan office area.
Power skirting is a type of skirting board that has power outlets built into it. It is a safe and attractive way to distribute power in an open plan office area.
Flush floor ducting is a type of ducting that is installed in the floor and has power outlets in it. It is a safe and hidden way to distribute power in an open plan office area.