Correct choice is (a) 2-10 bilayers of lipid
The explanation: OLV is also known as oligolamellar vesicles. These are made up of 2-10 bilayers of lipid surrounding a large internal volume which will be consisting of the drug. MLV is made up of a series of concentric bilayers of lipids. ULV is made of a single layer of lipids. There can be varying sizes from 20-40 nm to 1000 nm.