The relation between density, mass and volume is

1) to calculate = volume
given:
Density = 0.0915 g/ mL
mass = 17.7 grams
formula used:

Thus
Volume 
Answer: 193.44 mL
2) the mass of sample will be

Answer: 7 g
The partial pressure of hydrogen is 0.31 atm
calculation
find the number of hydrogen moles the container, that is
25/100 x 6.4 =1.6 moles of hydrogen
find the partial pressure for hydrogen in 1.6 moles
that is 6.4 moles= 1.24 atm
1.6 moles= ?
by cross multiplication
1.6moles x1.24 atm/ 6.4 moles= 0.31 atm
Possibly wet and unstable
The correct answer should be B.
The correct answer would be B.