40.What does the second paragraph mainly discuss?

(A)The Milky Way

(B)Major categories of galaxies

(C)How elliptical galaxies are formed

(D)Differences between irregular and spiral galaxies

41.The word "which"in line 7refers to

(A)dust

(B)gas

(C)pattern

(D)galaxy

42.According to the passage,new stars are formed in spiral galaxies due to

(A)an explosion of gas

(B)the compression of gas and dust

(C)the combining of old stars

(D)strong radio emissions

43.The word "symmetrical"in line 9is closest in meaning to

(A)proportionally balanced

(B)commonly seen

(C)typically large

(D)steadily growing

44.The word "obvious"in line 10is closest in meaning to

(A)discovered

(B)apparent

(C)understood

(D)simplistic