Genetic engineering is possible,because

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 :

Which of the following can be considered as molecular scissors?

During 'gene cloning',which is called a gene taxi?

The $Ti$ plasmid of $Agrobacterium$ $tumefaciens$ stands for

In genetic engineering,the reason for using restriction endonucleases is that ...