单项选择题
A large group of stars revolving around a center is known as a（）.
A.cluster B.shower C.constellation D.galaxy
单项选择题 A group of stars which appear close together and form a striking configuration such as a person or animal is a（）.
单项选择题 A first magnitude star is（）.
单项选择题 A double star is a star that（）.
