# Choose the correct statements concerning spectral classes of stars. (Give ALL correct answers, i.e., B, AC, BCD...) A) Neutral hydrogen lines dominate the spectrum for stars with temperatures around 10,000 K because a lot of the hydrogen is in the n=2 level.   B) Hydrogen lines are weak in type O-stars because most of it is completely ionized.   C) Oh Be A Fine Guy/Girl Kiss Me, is a mnemonic for remembering spectral classes.   D) The spectral sequence has recently been expanded to include L, T, and Y classes.   E) K-stars are dominated by lines from ionized helium because they are so hot.   F) The spectral types of stars arise primarily as a result of differences in temperature.

Question
Choose the correct statements concerning spectral classes of stars. (Give ALL correct answers, i.e., B, AC, BCD...)

A) Neutral hydrogen lines dominate the spectrum for stars with temperatures around 10,000 K because a lot of the hydrogen is in the n=2 level.

B) Hydrogen lines are weak in type O-stars because most of it is completely ionized.

C) Oh Be A Fine Guy/Girl Kiss Me, is a mnemonic for remembering spectral classes.

D) The spectral sequence has recently been expanded to include L, T, and Y classes.

E) K-stars are dominated by lines from ionized helium because they are so hot.

F) The spectral types of stars arise primarily as a result of differences in temperature.