In a certain code,
'big grand wedding' is coded as 'rc af bg'
'grand birthday celebration' is coded as 'kp vg rc'
'enjoy big celebration' is coded as 'af zd vg'
(all the codes are two letter coded only)

What is the possible code for ‘birthday bash’?

To find the possible code for 'birthday bash', let us analyze the given coded sentences step-by-step:

1. 'big grand wedding' is coded as 'rc af bg'

2. 'grand birthday celebration' is coded as 'kp vg rc'

3. 'enjoy big celebration' is coded as 'af zd vg'

Let's compare the sentences to identify the code for each word:

- Comparing sentence (1) and sentence (2): The common word is 'grand' and the common code is 'rc'. Therefore, the code for 'grand' is 'rc'.

- Comparing sentence (1) and sentence (3): The common word is 'big' and the common code is 'af'. Therefore, the code for 'big' is 'af'.

- Since the code for 'grand' is 'rc' and 'big' is 'af', from sentence (1), the remaining word 'wedding' must be coded as 'bg'.

- Comparing sentence (2) and sentence (3): The common word is 'celebration' and the common code is 'vg'. Therefore, the code for 'celebration' is 'vg'.

- In sentence (2), we have the words 'grand', 'birthday', and 'celebration' coded as 'kp vg rc'. Since the code for 'grand' is 'rc' and 'celebration' is 'vg', the remaining word 'birthday' must be coded as 'kp'.

Now, we need to find the possible code for 'birthday bash':

- We know the code for 'birthday' is 'kp'.

- The word 'bash' is a new word that does not appear in any of the three given sentences. Therefore, its code must be a new two-letter code that has not been used in the given sentences (i.e., it cannot be 'rc', 'af', 'bg', 'kp', 'vg', or 'zd').

- Looking at the option 'kp tn', 'kp' is the code for 'birthday', and 'tn' is a new code that does not appear in the given sentences. Thus, 'kp tn' is a possible code for 'birthday bash'.

Therefore, the correct option is kp tn.