Which of the following is not a cause of the error that could occur in Hartman and Braun oxygen analyzer based on the magnetic wind?

• A. The filament temperature could be affected by changes in thermal conductivity of the carrier gas
• B. Hydrocarbons in sample stream may react on the heated filaments
• C. Gravitation chimney flow effect lead to errors when cross tube is horizontal
• D. Combustible gases may react on the heated filaments