My guess is they need it to turn co2 into oxygen
Looking at decibel scale tables on internet, a "quiet whisper 1 meter away" is generally reported to have a sound intensity of about 20 dB, while a jackhammer 3 meters away produces a sound of about 100 dB of intensity, so option a) could be the correct one.
However, the other options could be considered correct as well, because without knowing the exact sound power produced by the whisper or by the jackhammer it's impossible to calculate the exact sound intensity with precision, and since the values reported in the three options are very similar, all the three of them can be considered as valid.
90.2 m/s. A rock dropped from rest after it has falling for 9.2 seconds will have a velocity of 90.2m/s.
The bodies left in free fall increase their speed (downwards) by 9.8 m/s² every second. The acceleration of gravity is the same for all objects and is independent of the masses of these. In the free fall the air resistance is not taken into account.
v = g*t
v = (9.8m/s²)(9.2s) = 90.2 m/s
5 ml = 0,05l
Work = Pressure * (Volume difference)
W= 2 * (V2 - V1)
W= 2 * (4,95)
