Self doubt:Pumping Lemma

Question

How by Pumping Lemma we can prove that

“context free grammar generate an infinite number of strings”

and here what could be pumping length ?

Answer 1

The pumping length would be $b^{V+1}$ where b is the maximum no of symbols on the right hand side of a production and V is the number of variables in the Grammar.

Comments

Can u explain more @Arkaprava

I am unable to get u 

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Please see this video, it'd be clear
https://youtu.be/IpgZB4elzX4