How does carbaminohemoglobin form and what role do hemoglobin's subunits play in this process?

• A. Carbaminohemoglobin forms when carbon dioxide binds to the free alpha amino groups on hemoglobin's subunits.
• B. Carbaminohemoglobin forms when oxygen binds to the free alpha amino groups on hemoglobin's subunits.
• C. Carbaminohemoglobin forms when carbon dioxide binds to the heme groups on hemoglobin's subunits.
• D. Carbaminohemoglobin forms when oxygen binds to the heme groups on hemoglobin's subunits.

Answer: (A)