Unfortunately I don't work with the same units as put forward in this question but the equation I use for this is:
pressure*volume = moles*8.314*temperature
The units required for this equation are:
pressure in pascals
temperature in Kelvin
volume in m³
If you convert the units in the question to the units for this equation, you'll be able to work out the volume of oxygen gas in m³
The speed of sound depends upon
a) air density
b) temperature
c) pressure
d) humidity
so there can be different reasons that the instrument goes out of tune outside.
However in the given options the best is The speed of sound decreases with a decrease in temperature.
C. 25 Miles
This is because you have 12.5 moles of water and using the ratio this is 2 (molar ratio). Therefore the molar ratio for HF is 4, so 12.5 x 2 = 25 moles