Explanation:

To determine the word represented by 'zay', we must analyze the common elements across the coded statements. From statement (I), 'may day zay' translates to 'good little dog'. From statement (II), 'jay cay zay' translates to 'girl behaves good'. By comparing these two statements, we observe that the common code word is 'zay', and the common English word is 'good'. Therefore, 'zay' represents 'good'. Let's examine the other options: Option A, 'behave', is part of 'girl behaves good' (II), but its corresponding code is not 'zay'. Option B, 'fell', is found in 'little girl fell' (IV), but its code is not 'zay'. Option D, 'dog', is present in 'good little dog' (I), but its code is not 'zay'. Thus, based on consistent comparison, 'good' is the only word represented by 'zay'.