### Pop Quiz

Which of the following best describes the Hairy Ball Theorm?

a) "Like, if you want me to do that, you need to wax just like I do."

b) There is no nonvanishing continuous tangent vector field on the sphere. Or, less briefly, if f is a continuous function that assigns a vector in R3 to every point p on a sphere, and for all p the vector f(p) is a tangent direction to the sphere at p, then there is at least one p such that f(p) = 0.

c) There is always a place on Earth where the air is perfectly still.

d) It explains why female tennis players grunt so loudly during serve.

Answer.

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