An inorganic compound (A) made of two most occurring elements in the Earth's crust and used in building construction, when made to react with carbon, forms a poisonous gas (B) which is most stable diatomic molecule, compound (A) and (B) are

Step-by-step solution

Silicon ( Si ) and oxygen ( O ) both are present in Earth's crust and used in construction (in the form of SiO ₂ ). SiO ₂(A) i.e. silicon dioxide is used in the building construction to produce concrete. In its crystalline form it is used in hydraulic fracturing. When SiO ₂ react with carbon, it will form CO and silicon, it is called a displacement reaction because carbon is more reactive, than silicon. As a result CO , a poisonous diatomic gas formed.