How to find standard deviation with ONLY sample size?

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So I have this weird math question, that I don't think gives enough information.

Find the standard deviation of the sample proportion for a sample of size 150, when we assume equal probabilities for the wins and losses of a football tournament. Assume also, that the number of outcomes in the population ( N) is very large, essentially infinite.

So I know that finding the standard deviation using sample proportions would be: sq root: pq/n, meaning the equation would be:

square root of: (the mean*(1-mean)/150 )

How would I compute the standard deviation with equal probabilities while the population is infinite?

These are the potential answers:

a.  0.12
b.  0.50
c.  0.002
d.  0.25
e.  0.041