Final answer:
The turns ratio for individual 1-phase transformers connected to form a 3-phase transformer bank can be found by multiplying the primary turns by the secondary turns.
Step-by-step explanation:
The turns ratio for individual 1-phase transformers connected to form a 3-phase transformer bank can be found by dividing the secondary turns by the primary turns. So, the correct option is C. Multiply the primary turns by the secondary turns.