big o doubt

Question

1/n   =  O(1)    is this relationship valid always

Comments

for n>0 yes it is valid

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if question would have been given two function  1/n   and 1 

which is correct

a)  1/n = Ω(1) 

b)  1  =  O(1/n) 

c) 1/n = O(1) 

so  answer will be c because while compairing function  we will go for very large value of n  in that case answer = c  ?? right sir  @ Tesla!   

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yes answer will be C

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thnku