Answer:
b. SaaS
Step-by-step explanation:
The full form of SaaS is software as a service. It is a software which is to be paid by per user rather than buying the outright of the software. It is a subscription based where the user must have to pay the subscription fees on a monthly or yearly basis. When the subscription tenure is expired the user must have to pay the charges again to take the service
Therefore the option b is correct