Compared to the Sun, older stars contain what proportion of ...

[Davideckstein7]

Compared to the Sun, older stars contain what proportion of elements heavier than hydrogen and helium?
 
  A) a higher proportion
  B) exactly the same proportion
  C) they contain absolutely no heavy elements at all
  D) a lower proportion

Question 2

At present the universe is expanding, but we are not certain if this expansion will continue forever, come to a stop, or if the universe will ultimately collapse back into itself.
 
  What observational tests are possible to test among these three possibilities?

[Mholman93]

Answer to Question 1

D

Answer to Question 2

The possibilities can be tested by measuring the density of the universe. If the density is too low the universe expands forever; if too high the universe stops and collapses. Also, measuring the amount by which the rate of past expansion differed from the current rate (by studying redshifts) can reveal the rate at which expansion is slowing and so what will happen.

[Davideckstein7]

Gracias!

[dawsa925]

Excellent