In the first and second statements, the common code-words are ‘cin’ and ‘si’ and the common words are ‘her’ and ‘is’. So, ‘cin’ and ‘si’ are the codes for ‘her’ and ‘is’. In the second and third statements, the common code-words are ‘cin’, ‘si’ and ’oin’ and the common words are ‘her’, ’is’ and ‘poetry’. So, ‘oin’ stands for ‘poetry’.