Identify the wrong statement with regard to Cloning vectors:

Cloning vector needs to have a large number (minimum 20) of recognition sites for the commonly used each restriction enzymes.

Cloning vector must have an origin of replication

Retroviruses are used to transfer genes into animals 

It is a small piece of DNA that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for cloning purposes.