Final answer:
The two most abundant elements in the Sun are hydrogen and helium. Hence options B and D are correct.
Step-by-step explanation:
The two elements most abundant in the Sun are hydrogen (b) and helium (d). Hydrogen constitutes approximately 74% of the Sun's mass, and helium makes up around 24%. These two elements dominate the Sun's composition due to the processes occurring in its core, primarily nuclear fusion. Hydrogen nuclei fuse to form helium through a series of nuclear reactions, releasing immense amounts of energy in the form of light and heat, which sustains the Sun's luminosity. The high temperatures and pressures at the Sun's core facilitate these fusion reactions. Although other elements, including oxygen and nitrogen, are present in trace amounts, hydrogen and helium overwhelmingly dominate, defining the Sun's elemental composition and powering its radiant energy.