_____ is the location in the H-R diagram where stars first reach ...

[j.rubin]

_____ is the location in the H-R diagram where stars first reach stability as hydrogen-burning stars.
 
  A) The proton-proton chain
  B) The carbon-nitrogen-oxygen cycle
  C) The zero-age main sequence
  D) The interstellar medium region

Question 2

The Sun fuses _____ hydrogen nuclei to make one helium nucleus.
 
  A) two
  B) three
  C) four
  D) five

[britb2u]

Answer to Question 1

C

Answer to Question 2

C

[j.rubin]

Thanks for the timely response, appreciate it

[flexer1n1]

Gracias!