In a Study by Sheiham Et Al

In a study by Sheiham et al. (2002) of 'the relationship between oral health status and body mass index among older people' in Great Britain, Fisher's exact test was used Why would this test have been used in this instance?

A) An adjusted odds ratio would not provide a valid effect size.
B) An adjusted odds ratio could not be used as the sample was too large.
C) An adjusted odds ratio could not be used as the sample was too small.
D) none of the above.