Final answer:
The structure of wrought iron is deemed unreliable primarily due to its fibrous structure within the ferrite, making it less consistent in strength and ductility compared to metals properly alloyed and treated for applications requiring high strength. Option B is correct.
Step-by-step explanation:
The structure of wrought iron is considered unreliable because it has a fibrous structure in the ferrite. This fibrous structure can lead to inconsistencies in strength and ductility, which can compromise its reliability.
Iron is a metal with certain properties such as being solid, shiny, and a good conductor of electricity and heat. However, wrought iron, when all the carbon is removed from iron to make it pure, becomes quite soft, easily worked, and lacks structural strength, making it less suitable for applications that require reliable, high-strength materials.
Metals, in general, exhibit characteristics such as shininess, good electrical and heat conductivity, and are malleable and ductile.
These attributes make metals like iron when alloyed with small amounts of carbon (e.g., in mild steel), suitable for a variety of structural applications.
On the other hand, wrought iron's reliable structure is in question precisely because it is devoid of these strengthening impurities.
Additionally, the heat treatment process plays a critical role in determining the mechanical properties of metals. In the case of wrought iron, the lack of proper heat treatment can lead to an unreliable structure.
The heat treatment would thus be necessary to enhance its properties for certain applications.
Hence, option B is correct.