1. Steller stated that "some of the Stars have more mass at the stage of main sequence than the Sun, but towards the end stage it loses almost more than seven times of the solar mass". If the star is in the main sequence. then it undergoes nuclear fusion process. Due to this, the star mass is tightly bounded by high gravitational forces and does not have any chance to lose mass. Towards the end stage. the star becomes a white dwarf and it loses lot of material in the form planetary nebula. There might be another chance to lose material, when it turns to a white dwarf. Hence, at the end stage of the star does not undergoes any nuclear fusion reaction. so the star cannot maintain the same mass at the both stages.
2. (c).The light emitted from the event horizon of the black holes
3. (a),It would double in strength
4. (b).The gas and dust cloud condensed to form sun and protoplanetary disc in which the planets was formed.

5. For the terrestrial planets to form

a) planetesimals had to accrete to make the protoplanets

b) protoplanets had to collide and fragment each other into smaller pieces

c) protoplanets had to sweep up light elements

d) planetesimals had to collide and fragment each other into smaller pieces

6. Because of the temperatures in the protoplanetary disk, a. rocks, metals, and ices (hydrogen compounds) froze in the inner region only b. rocks and metals froze in both the inner and outer regions, and ices froze only in the outer region c. rocks and metals froze in the inner region only, and ices froze in the outer region only d. rocks and metals froze in both the inner and outer regions, and ices and H and He gases froze only in the outer region