Quiz number theory doubt

If a Person has an infinite number of red, blue and yellow socks in a drawer, how many minimum socks must he pull out of the drawer to guarantee he has a pair?

Sir , Any explanation for this question? How to solve it

In a complete tree of N nodes Also this one: The no of nodes at a level at height h from bottom is approximately equal to : ?

@shivampandey9599 in socks one well worst case first three all different so at 4th it is guaranteed pair is formed so ans is 4.
for second questions options coz there was some error in this question some time before

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