This is due to earths location in the solar system. Earth is in the habitat zone or the Goldie locks zone, in this zone it's not too hot or not too cold for water to exist. Other planets in different star systems have liquid oceans due to them being in the habitat zone.
It might be to late but the answer is C
Try the solutions described in the attached picture, note the answers are marked with green colour.
Answer:
distance between seats = 2*11.10 = 22.20 m
Explanation:
seats row is parallel to a stage with a distance d = 90 m
doorway width = 0.070 m
speaker frequency = 4.00 * 10^4 Hz
Speed of sound = 343 m/s
tone will be heard at

we know that 
so





[tex]x = d*tan\theta = 90*0.1234 = 11.10 m
distance between seats = 2*11.10 = 22.20 m