Imagine that you are surveying the sky, and take images of two galaxies. Galaxy A looks twice as wide as Galaxy B - i.e. it subtends twice the angle as viewed from the Earth, with an apparent radius of twice as many pixels.
Which one of these statements cannot be true?
If the two galaxies are really the same size, B must be twice as far away as A.
If the two galaxies are at the same distance from the Earth, B must be half the size of A
.If galaxy B is really twice as large as A, it must be four times further away.
If galaxy A is really four times as big as galaxy B, it must be twice as far away.
If galaxy B is really half the size of galaxy A, it must be twice as far away.