Hi Sambasiva, Pick a subject that shows you like challenge and enjoy learning, even if it's maybe not your all-time favorite subject. Though you should always be honest and accurate in a job interview, it doesn't hurt to polish you answers, tailoring them to fit the situation. The employer wants to know you're dependable, teachable and enjoy the challenge of work. Pick any subject that challenges you and shows you like figuring more out about the world.

Hope that solves your query,
Feel free to post more queries,
Thanks & Good luck.