Answer
(a) greater than
(b) I
Work Step by Step
(a) We know that the escape speed of the Earth is greater than that of the Moon, hence the amount of energy required to get a spacecraft from the Earth to the Moon is greater than the energy required to get the same spacecraft from the Moon to the Earth.
(b) We know that option(I) is correct -- that is, the escape speed of the Moon is less than that of the Earth; therefore, less energy is required to leave the Moon.