Final answer:
The correct representation is option (a) |z - y| < d.
Step-by-step explanation:
The correct representation of the statement 'z is less than d units from y' is option (a) |z - y| < d.
To understand this, let's break it down. The expression |z - y| represents the absolute value of the difference between z and y. When this absolute value is less than d, it means that the distance between z and y is less than d units.
For example, if z = 4 and y = 8, and d = 6, then |z - y| = |4 - 8| = |-4| = 4, which is less than d. Therefore, option (a) is the correct representation.