Organic Chemistry A. Hydrocarbons

Methane ($CH₄$) was a primary component of the early atmosphere.

Hydrogen Cyanide (HCN) is a simple, highly reactive molecule that could form from methane and ammonia. It's a key precursor in the synthesis of more complex organic molecules.

Nitrile (R-C≡N) is a functional group that can be formed from HCN and other simple molecules. It's an intermediate step.

Amino Acids are the building blocks of proteins and are more complex molecules that could have formed from simpler precursors like HCN and nitriles in the "primordial soup."

The correct sequence of their appearance under simulated primitive earth conditions is Methane, Hydrogen Cyanide, Nitrile, Amino Acid.

Carbon is the fundamental element of all organic compounds (including bio-compounds). Organic compounds are a large class of chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements, most commonly hydrogen, oxygen, or nitrogen which allows for the creation of incredibly diverse and complex molecular structures, which are the basis of all known life.

Carbon is the fundamental element of all organic compounds (including bio-compounds). Organic compounds are a large class of chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements, most commonly hydrogen, oxygen, or nitrogen.

Molecular weight increases with the number of carbon atoms.

Methane (​CH₄): 1 carbon atom (MW ~ 16)

Ethane (​C₂H₆): 2 carbon atoms (MW ~ 30)

Propane (C₃H₈): 3 carbon atoms (MW ~ 44)

Butane (C₄H₁₀): 4 carbon atoms (MW ~ 58)

So, the increasing order of molecular weights is Methane < Ethane < Propane < Butane.