Both options you indicated are B1/B2 Visa (Business/Tourism) Visa. There is no difference in between them.
In any case, you need to convince the Visa officer that you are going to come back to India. So I suggest you ask your parents to produce Pay Stubs for you and to open a bank account and put some money in it.
The fact that you are unmarried is against.
I also suggest that you don't tell the Visa officer that you are going for the CS exam, just tourism with your mom and sister, this would make it easier.
Your status does not matter when you go for the CS exam, all they want is your passport and they don't care which visa you have.