In a coded language, 'CAT' is coded as '312', 'DOG' as '415', and 'BAT' as '213'. What is the code for 'TAD'?

Answer: B. 321
The common letters 'A' and 'T' in 'BAT' and 'CAT' help establish that 'A' = 1 and 'T' = 3. 'D' from 'DOG' is 4, so 'TAD' = 321.