C++ MQCs with Explanation ( WORKING WITH FILES)

The following is a list of header lines for creating function templates. Which of them is legal?

1. template < class T > swap ( T & x, T & y)
2. template < T > void swap (T & x, T & y)
3. class < template T> void swap (T & x, T & y)
4. None of the above

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Answer: 

Option b: template < T > void swap (T & x, T & y)

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Explanation Here