Investment in Post Office time deposit is: (i)Zero risk investment (ii)Low risk investment (iii) Medium risk investment (iv) High risk investment

If it is so , then when the risk is high?

I strongly agree with Sahar Alech. There is no investment without a risk so my answer would be this investment is low risk.

the well answer isZero risk investment 

answer option >>>>>>>>>>>>>>>>>>>>>>>>>      (i)Zero risk investment

I see that the best option is    High risk investment

There is nothing like "Zero Risks". Some risks are rare in nature and are classified as unforeseen & unpredictable. Hence "Low Risk" is the correct option in this case.

Already Answered...

To the best of my knowledge (i)Zero risk investment 

Low risk investment.............................

(i)Zero risk investment

That's one of service requirements, you will get back after all.