Answer:
The correct option is 3.
Step-by-step explanation:
In a one-to-one function every element of the function's codomain is the image of at most one element of its domain.
A function is one-to-one function if it passes vertical line test and horizontal line test. It means each vertical and horizontal line cuts the graph of function at most 1.
The given graph passes the vertical and horizontal line test. It means there exist one output for every input. So the function shown in the graph is one-to-one function.
Therefore, the correct option is 3.
