Question

Which function is NOT continuous?

Answer 1

Number of tennis balls that can fit completely inside a particular box as a function of the radius of the tennis balls. C

Answer 2

C is not continuous. 

Continuous functions have connected graphs; this indicates that every possible value of x has a value of y associated with it.  In this case, that says that every possible radius measurement has a number of tennis balls associated with it.  The problem with this is that we cannot have a fractional part of a tennis ball, so it is not continuous.