I have a friend in Mumbai who is ____ actress.

To choose the correct article, we must consider the sound that follows, not just the spelling. The word 'actress' starts with the sound /æ/, which is a vowel sound. Therefore, we use 'an' before it. Option A uses 'a', which is used before consonant sounds. Since 'actress' begins with a vowel sound, 'a' is incorrect. Option B uses 'an', which is correct for vowel sounds. This makes it the appropriate choice. Option C uses 'the', which is used for specific or known nouns. Here, the actress is not specified, so 'the' is incorrect. Option D says 'More than one of the above', but only one option is correct, so this is incorrect. Option E says 'None of the above', but since 'an' is correct, this option is also incorrect. Therefore, the correct choice is 'an'.