1) a hot, bright star would appear in which section of an h-r diagram ? a) lower left b) upper right c) upper left d) lower right 2) all stars remain on the main sequence a) until they stabilize b) for about 90% of their lifetimes c) until they become protostars d) for about 10 billion years

Answer 1) Option C) Upper Left

Explanation : Hertzsprung-Russell (or H-R) diagrams are a graphical tool used to classify the stars according to their brightness (luminosity), spectral type and hotness (temperature) . In this diagram the stars which are found to be hot and bright are placed on the top left upper corner. Stars which are in the stable phase of hydrogen burning lie along the Main Sequence according to their mass.

Answer 2) Option B) for about 90% of their lifetimes

Explanation : It is found that the main sequence stars spend their 90% of lifetime fusing hydrogen into helium. These main sequence stars burns the hydrogen present in its core, until it reaches the end of its life cycle. At this point, it leaves the main sequence.

Hence, It spends 90% of its lifetime in the main sequence.