If 'APPLE' is coded as '13524', 'BANANA' as '214321', and 'LEMON' as '52413', what is the code for 'NANA'?

Answer: C. 2143
The common letters 'A' and 'N' in 'BANANA' and 'LEMON' help establish that 'A' = 1 and 'N' = 2. Thus, 'NANA' = 2143.