Correct option is A)
The 'star' refers to all the existing stars. The Sun is one of these stars. The articles 'a' and 'an also mean 'one'. 'An' is used when the noun begins with a vowel, and the star begins with a consonant, hence the correct option is 'a' and 'an' is the incorrect option. 'The' is an incorrect answer because the sun isn't the only star. The option D is incorrect because an article is required in the given statement as we are not referring to the star in a general sense.