Light from the stars, because the orbits make it difficult to see them.
Answer
a) For the rock






b)
for maximum range




c) The value of θ is the same on every planet as g divides out.
As far as I know acids turn litmus paper red and bases turn it blue. on the pH scale anything under 7 is acid and above is base so I think it is A. I am not totally sure, but that is the best answer I can give you! Good Luck! Hope this helps!!