I have completed my bachlor degree in computer science now want to do master's..Which option should choose for PhD studies? Please suggest

Whatever subject interests you and there is funding for. If you don't know what to do, choose a general masters in computing and go from there.

Thank you for your valuable suggestion

Hey, I guess this article will answer all your questions. Your interest in the subject, feasibility of the research, your potential and skills are some of the factors that play a very important role here.

https://www.enago.com/academy/choose-good-research-topic-phd/