A star has a spectrum with lines indicating the presence of ionized helium. This star should be classified as a(n) <u>O</u> type star.
Explanation:
Helium is a noble has. Its formation and ionization requires high temperature which is possible only in core of stars. Stars classified based on temperatures. Type O stars have very high temperatures (more than 30,000 K). At these temperatures, Helium gets ionized. Thus, the spectrum of O-type stars indicates the presence of ionized helium more than the neutral.
