The correct option is
A Called
Option B: 'Call' means 'to name or address someone or something as'. The word completes the sentence in meaning: 'Bali is often called (named as) the island of Gods'.
Hence option B is correct.
Option A: 'As' means 'for example', or 'in comparison to'. The word does not complete the sentence in meaning.
Option C: 'Known' means 'to be acquainted with'. It would be followed by the word 'as' in this sentence: 'Bali is often 'known as' the island of Gods.'
Otherwise, the sentence formed is incomplete.
Option D: 'Told' means 'given an account of or information about'.
The meaning is irrelevant to the sentence.
Hence options A, C and D are incorrect.