(1) Organic matter refers to carbon-containing compounds, and combustible polyurethane (PU) plastics are organic polymer synthetic substances or organic matter;

(2) The condition of combustion is that the temperature reaches the ignition point of combustible materials and contacts with oxygen, so fire extinguishing is the condition of controlling combustion. Water fire extinguishing is mainly to reduce the temperature of combustible substances below their ignition point, thus playing a role in fire extinguishing. When a fire breaks out in a high-rise residential building, the correct way to escape is to take the safe passage, and never take the elevator.

(3) In order to prevent fire, attention should be paid to whether the decorative materials are flammable and resistant to high temperature when choosing decorative materials;

(4) According to the fact that metal materials generally include metal elements and alloys, it can be known that cast iron pipes are metal alloys, copper pipes belong to metal elements, both of which are metal materials, while plastic pipes are organic synthetic materials rather than metal materials;

(5) The protection methods of metal resources mainly include: preventing metal corrosion, recycling waste metals, and rationally exploiting minerals. The metal activity of silver is weaker than that of iron and copper, so both of them can replace silver in silver nitrate, and the activity of iron is stronger than that of copper, so iron participates in the reaction of replacing silver first, so the solid residue must contain silver. When the amount of iron is large, the solid may contain iron, but whether copper contains it depends on the amount of iron. Analysis option b is incorrect;

So the answer is: (1) organic;

(2) Reduce the temperature of combustible materials; Escape from the safe passage;

(3) non-combustion; High temperature resistance;

(4) A and B

(5) metal painting to prevent rust; b；