Given point Q(4, 7). We need to find the perpendicular distance of this point from the y-axis.

Explanation:
Perpendicular distance of a point from the y-axis is the distance between the point and the y-axis measured along a line perpendicular to the y-axis.

Let's draw a rough sketch to understand this better:

We can see that the point Q(4, 7) lies on the right side of the y-axis. Therefore, the perpendicular distance of this point from the y-axis will be the distance between the point and the y-axis measured along a line perpendicular to the y-axis.

We can draw a perpendicular line from the point Q(4, 7) to the y-axis as shown below:

The length of this line represents the perpendicular distance of the point Q(4, 7) from the y-axis.

Now, we need to find the length of this line.

We know that the y-axis is a vertical line passing through the origin. Therefore, the x-coordinate of any point lying on the y-axis is zero. In other words, the y-axis intersects the x-axis at the point (0, 0).

Let's mark the point (0, 0) on the graph:

We can see that the point Q(4, 7) is 4 units away from the y-axis (which is the vertical line passing through the point (0, 0)).

Therefore, the perpendicular distance of the point Q(4, 7) from the y-axis is 4 units.

Hence, the correct answer is option 'A' (4 units).