The partial pressure of hydrogen is 0.31 atm (answer A)
calculation
partial pressure of hydrogen = moles of hydrogen/ total moles of gas x total pressure.
moles of hydrogen = 25% of total moles
that is = 25/100 x 6.4 =1.6 moles
total moles of gas = 6.4 moles
partial pressure of hydrogen is therefore = 1.6 moles/6.4 moles x 1.24 atm =0.31 atm