Can some pls help me with this and explain?

Nuclear fusion is the source of energy for stars. besides hydrogen, which other element is most likely also common in stars?

Which statement best describes the relationship between period and frequency of light waves? a) in wave b the period increases and the frequency decreases from wave a. b) in wave a the period increases and the frequency decreases from wave b. c) in wave b the period is shorter and the frequency is greater than in wave a. d) in wave a the period is shorter and the frequency is greater than in wave b.

Can someone me with 1 to 4 plz. fast