premise: A stylish woman in black poses in front of graffiti on the sidewalk. hypothesis: A fashionable lady poses by the graffiti.
entailment: Stylish and fashionable are synonyms; 'lady' is a polite synonym for 'woman'; since she poses in front of graffiti she is therefore by graffiti; there is only one mention of graffiti, so 'the' is appropriate.