What is the critical temperature at which hydrogen can fuse into helium in the star’s core?

A.5,800 K
B.26.000 K
C.One million K
D.Ten million K
E.100 million K

Please research your questions at the following links I located for you:

http://en.wikipedia.org/wiki/Stellar_evolution

http://spiff.rit.edu/classes/phys230/lectures/star_age/star_age.html

http://en.wikipedia.org/wiki/Main_sequence

http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html