ANS:B - less than

Explanation: An oxy-hydrogen flame is created by burning a mixture of hydrogen and oxygen gases. The temperature of this flame is around 2800 °C (5072 °F) which is still high, but lower than the temperature of an oxy-acetylene flame. On the other hand, an oxy-acetylene flame is created by burning a mixture of acetylene and oxygen gases. The temperature of this flame is around 3100 °C (5600 °F). Acetylene is a hydrocarbon gas with a triple bond between its carbon atoms, which makes it more reactive and burns hotter than hydrogen. In summary, the temperature of an oxy-acetylene flame is higher than that of an oxy-hydrogen flame because acetylene is a more reactive gas that burns at a higher temperature than hydrogen.