The graph which is a one-to-one function is:
Graph B
<h2>Step-by-step explanation:</h2>Function--
The graph of a function must always pass the vertical line test i.e. any line passing through the domain and parallel to the y-axis must pass through the graph exactly once.
and also for a function to be<em> one-one</em> the graph of the function must pass horizontal line test i.e. any line passing through the co-domain and parallel to the x-axis must intersect the graph at most once.
In the given graphs :
Graph A is not a function, since it does not pass the horizontal line test and hence we won't talk about being a one-one function.
Graph B is a function as well is one-one since it passes horizontal as well as vertical line test.
Graph C is a function but is not one-one as it fails the horizontal line test.
Hence, the correct answer is:
Graph B
