Which of the following hydrolases cleaves internal phosphodiester bonds in a polynucleotide chain?

What is the term for a molecule that carries a desired gene into a host cell for cloning?

An enzyme catalyzing the removal of nucleotides from the ends of $DNA$ is

Consider the following statements:
$I.$ $A$ soil-inhabiting plant bacterium,$Agrobacterium \; tumefaciens$,a pathogen of several dicot plants,is able to transfer a piece of $DNA$ known as $T-DNA$.
$II.$ The $T-DNA$ causes tumours.
$III.$ Tumour formation is induced by $Ti-plasmid$.
Which of the statements given above are correct?

Which of the following is known as the natural genetic engineer?

In $EcoR\, I$,what do the letters $E$ and $R$ stand for,respectively?