Question

science ka important q kya hai 10 class ke liye

And
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Answer 1

Hey!! Pls solve the sample papers of oswal/arihant . U'll.get many imp. ques. there

Answer 2

I think you should revise the important questions which appeared earlier in cbse boards;you will get it from cbse site itself.
and all chapters are important but dont spend too much time on easy chapters like our environment,management of natural resource and sources of energy
because only 1 or 2 mark questions may come!!
and all the best for science!!