The correct options are
B A constellation does not change its shape every day.
D In cities, it is tough to find constellations due to pollution.
A constellation can be any cluster of stars which makes sense by making a recognisable shape to someone. It may not make sense to others. People may give the same collection a different name according to how they imagine that collection to be. Ursa Major is also called the Big Dipper, and some may call it the Great Bear. A star is very far while their movement is negligible, so we can say they don't move; thus, they don't change the shape of constellations. Stars are everywhere in the universe. We can see them from anywhere on the Earth.