Hello student,

KVPY is a tough examination which requires a research based mindset and all the basics and concepts cleared thoroughly. There may be times when you wont be able to solve some questions just like this, so, dont get depressed and keep trying and hunt for the solution. Due to these questions itself you brain will get trained to solve such challenging questions and you will get better at solving. Thus, keep practicing and never give up. You will then surely be able to crack the exam.

I hope this helps, All the Best!