20. When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts. The outer shellof the star, which is still mostly hydrogen, starts to expand. At this phase the star is called a . a. White dwarf
b. Red dwarf
c. Red Giant
d. Black hole

Si una estrella no tiene paralaje medible, ¿qué puedes inferir?

Which is true of a liquid? it has a definite volume but not a definite mass. it has a definite mass but not a definite volume. it has a definite volume but not a definite shape. it has a definite shape but not a definite volume.

16. in a reaction that has reached equilibrium, a. the forward and reverse reactions are occurring at the same rate. b. the reactants and products are in equal concentrations. c. the forward reaction has gone further than the reverse reaction. d. there are equal numbers of atoms on both sides of the equation. e. a, b, and d are correct.