Of the following primitive Earth conditions and chemical reactions, which one do biochemists know was important to the formation of amino acids and subsequent formation of complex carbon molecules that are common to life?
A. There had to be a reducing atmosphere rather than one with oxygen, otherwise formation of those molecules would have been extremely difficult.
B. There had to be an atmosphere with oxygen rather than a reducing atmosphere, otherwise formation of those molecules would have been extremely difficult.
C. Cellular respiration was necessary for the reducing atmosphere to form, otherwise photosynthesis would not have been able to occur.
D. Sulfide molecules from deep-sea vents interacted with available atmospheric oxygen, producing a reducing atmosphere that would have encouraged amino acid formation.
E. Silicate surfaces provide excellent substrates for cellular respiration, thus increasing the available atmospheric oxygen, which in turn promoted evolution of inorganic molecules into animate forms.
Answer: A