$A$ plasmid without a selectable marker was chosen as a vector for cloning a gene. How does this affect the experiment?

What modification is done on the $Ti$ plasmid of Agrobacterium tumefaciens to convert it into a cloning vector?

Identify the plasmid among the following.

$PCR$ technique was invented by

Which enzyme is known as molecular scissors?

Refer to the following statements for agarose-gel electrophoresis :
$(a)$ Agarose is a natural polymer obtained from sea-weed.
$(b)$ The separation of $DNA$ molecules in agarose-gel electrophoresis depends on the size of $DNA$.
$(c)$ The $DNA$ migrates from negatively-charged electrode to the positively-charged electrode.
$(d)$ The $DNA$ migrates from positively-charged electrode to the negatively-charged electrode.
Choose the most appropriate answer from the options given below :