An enzyme that makes a double stranded DNA copy from a single stranded RNA template molecule is known as
DNA polymerase
RNA polymerase
Reverse transcriptase
Phosphokinase
Reverse transcriptase is an RNA dependent DNA polymerase that produces ds DNA from RNA template. It moves along the template in 3' → 5' direction, synthesizing DNA is 5' → 3' direction.
It is seen in retro viruses (e.g. HIV).