Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
A transformer has two coils, electrically insulated from each other. One coil is called the primary coil and the other is called the secondary coil.


Question: A transformer has two coils, electrically insulated from each other. one coil is called the primary coil and the other is called the what?
secondary coil
secondary coil.