Answer:
B is a function.
Explanation:
A relation that is a set of points is a function if all the x's are different. Each ordered pair in the set (excluding the duplicates if any) all have to have a distinct x.
For example if someone ask you if this is a function they are trying to trick you:
{(4,5),(1,3),(4,5)}.
They are trying to trick you because they listed the element (4,5) twice.
The set is really {(4,5),(1,3)}.
This would be a function because all the x's are distinct, ex 4 is different than 1.
Let's look at your choices:
A This is not a function because you have two pairs with the same x-coordinate.
B This is a function. There are no repeats of any x,
C This is not a function because you have 11 as x twice.
D This is not a function because x=3 happens twice.
If the same x happens more than once than it isn't a function.