Harman wants C,C++ and OOPS concepts. But I know only about C(I’ve been learning it for one month now).
Should I accept it or not respond? Because once you attend a drive in a company and not get selected, you can’t attend the same company placement drive for 6 months.
@wali_3319673 Your input would be appreciated 
If you have just started learning C, I don’t think you should accept.
It is a development profile and they want candidates who are good with programming with Data Structures (Array, Linked List, Stack, etc)
Take time and prepare the skills.
Do NOT decline the interview with any other reasons, or they will not call you in the future. Not submitting any response is a better option.
@wali Thanks for your help! 