The answer is: C. The line is one iambic metrical foot
The iambic metrical foot is composed of an unstressed syllable followed by a stressed syllable, for example: So LONG / as MEN / can BREATHE / or EYES / can SEE; here all the lowercase words are the unstressed syllables and the uppercase words are the stressed syllables, in this case it would be this way: in-XAN-a-DU-did-KU-bla-KHAN