The distance of a point from the y-axis is the perpendicular distance between the point and the y-axis. In this case, we are given the point (-5, 6). Let's understand why the correct answer is option 'B' (5 units) by following these steps:

Step 1: Understanding the y-axis
The y-axis is a vertical line on the coordinate plane. It represents the values of the y-coordinate. The x-coordinate on the y-axis is always 0.

Step 2: Understanding the point (-5, 6)
The point (-5, 6) has an x-coordinate of -5 and a y-coordinate of 6. This means that the point is 5 units to the left of the y-axis and 6 units above the x-axis.

Step 3: Finding the distance from the y-axis
To find the distance of the point (-5, 6) from the y-axis, we need to measure the perpendicular distance between the point and the y-axis.

Step 4: Drawing a diagram
We can draw a diagram to visualize the point (-5, 6) and the y-axis.

| -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
------------------------------------------------------------
1 | .
2 | .
3 | .
4 | .
5 | .
6 | .
7 | .
8 | .
9 | .
10 | .

Step 5: Measuring the distance
From the diagram, we can see that the point (-5, 6) is 5 units to the left of the y-axis. Therefore, the distance of the point from the y-axis is 5 units.

Step 6: Conclusion
The correct answer is option 'B' (5 units) as the point (-5, 6) is 5 units to the left of the y-axis.