Answer: Option A. -> Cobalt
Cobalt is the binding material in cemented carbides

Answer: Option D. -> Cobalt
Cobalt improves strength at high temperatures and magnetic permeability.
Increases hardness, also allows for higher quenching temperatures (during the heat treatment procedure). Intensifies the individual effects of other elements in more complex steels. Co is not a carbide former, however adding Cobalt to the alloy allows for higher attainable hardness and higher red hot hardness.

Answer: Option A. -> 63 to 67% nickel and 30% copper
Monel metal contains 63 to 67% nickel and 30% copper

Answer: Option D. -> The chilled cast iron has no graphite
Chilled cast iron. Iron-carbon alloy with low graphitization factor so that chill occurs forming a graphite-free structure.
In order to achieve chilling, the silicon content is set to a low level depending on the wall thickness of the casting; the carbon content is approx. 2.5 to 3.8%.

Answer: Option A. -> Nickel, Chromium and Iron
Inconel is a family of austenitic nickel-chromium-based superalloys.
Inconel alloys are oxidation-corrosion-resistant materials well suited for service in extreme environments subjected to pressure and heat.

Answer: Option A. -> Increase hardenability
A small percentage of boron is added to steel in order to Increase hardenability

Answer: Option A. -> Copper and zinc
Brass is an alloy of Copper and zinc

Answer: Option A. -> Wholly pearlite
The steels which contains less than 0.8% carbon are known as hypo eutectoid steels. It consists of pearlite and proeutectoid ferrite.

Answer: Option D. -> Germanium
The transistor is made of Germanium

Answer: Option B. -> 50% or more iron
Steel contains 50% or more iron