Final answer:
The cloning vector used is a plasmid known as the modified Ti a) plasmid, which is used to create transgenic plants with desired traits such as herbicide resistance.
Step-by-step explanation:
The cloning vector used to transfer an herbicide-resistance gene from Agrobacterium to a plant cell is a a) plasmid. Specifically, the Ti plasmid, derived from Agrobacterium tumefaciens, is modified by researchers to remove the tumor-inducing genes and insert genes of interest, such as the herbicide-resistance gene.
This modified Ti plasmid is a shuttle vector that can be transferred into the plant genome, where the gene of interest then recombines into the plant cell's genome.
This process ultimately enables the production of transgenic plants with desired traits such as herbicide resistance.