If I study pure science in my graduate and under-graduate course, what are my career options?
I am really glad to see a student interested in pure science. There are lots of opportunities for students from pure science, especially in government institutions like defence, atomic energy etc. You can become scientist in the departments that I have listed above. Post B.Sc you could write GATE and get into premium institutions like IIT, IISc etc. to do your M.Sc/Ph.D. These institutions have world class research facilities and faculty. We need more people like you who are interested in pure science and research - to help solve some very big problems in India itself.
Once you finish graduation in pure science you can opt for a masters in a field that you want to specialize in for example aerospace,bio-tech
Based on your interest you can further go on to do research course(Like a PhD) in the field of interest
Best of luck for your future
I wanted to add to the other science-focused answers you already have that many other options will be available to you with those degrees! Many companies are now understanding the value of hiring individuals with a STEM background. I obtained degrees in physics and accounting because I love solving problems, so as long as you are able to explain how your coursework relates to the field or job that you are interested in then you will have a world of possibilities!