Which of the following statements is true of open clusters?
A) They contain 105 to 106 stars in a region about 10 pc in diameter.
B) They have a transparent appearance.
C) They comprise stars that are crowded together.
D) They are spherical.
Question 2
In the context of various observations made, which of the following statements is true of gamma-ray bursts?
A) They occur from one particular region in the sky.
B) They glow brightly and resemble novae.
C) Relatively long gamma-ray bursts are produced by a kind of supernova explosion.
D) Beams of intense radiation flowing into a star result in powerful gamma-ray bursts.