The star Vega, an A star, exhibits an absorption line spectrum with very strong hydrogen lines. Aldebaran, a K star, exhbiits an absorption line spectrum with very weak hydrogen lines. What is the reason for this difference? O a. Vega is closer to Earth than Aldebaran, so its spectrum lines appear stronger. O b. Aldebaran is an older star than Vega and has used up most of its hydrogen, leading to weak hydrogen lines. O c. Vega's surface temperature is cool enough (-4,500 K) to generate strong hydrogen lines. Aldebaran is too hot (-10,000 K) and therefore has weak hydrogen lines. O d. Vega's surface temperature is the right temperature (-10,000 K) to generate strong hydrogen lines. Aldebaran is too cool (-4500 K) and therefore has weak hydrogen lines. O e. Vega is a hydrogen-rich star, leading to strong spectrum lines. Aldebaran is a hydrogen-poor star, leading to weak spectrum lines.