You need to remember the formula that helps you to evaluate the average molecular speed of `O_2` such that:

`v = sqrt(3TR/M)`

R expresses Boltzmann's constant = `8.314 J*K^(-1)*mol^(-1)`

T expresses temperature in Kelvin

M expresses mass of 1 mole of oxygen

Notice that the problem provides the temperature in Celsius degrees, hence you need to convert from Celsius to Kelvin such that:

T = Celsius + 273.15

`T = 277 + 273.15`

`T = 550.15` Kelvin

You need to remember that the mass of 1 mole of oxygen is of 32 grams.

Substituting, 8.314 for R, 550.15 for T and 0.032 Kg for in formula of molecular speed yields:

`v = sqrt(3*550.15*8.314/0.032)`

`v = 654.833 m/s`

**Hence, evaluating the average molecular speed of `O_2` yields v = `654.833 m/s. ` **