Structured delivery is not a form of delivery.

Explanation:
Delivery refers to the transfer of possession of goods from one party to another. It is an essential element in the transfer of ownership. Different forms of delivery exist depending on the nature of the goods and the agreement between the parties involved.

The options provided are:
a) Constructive delivery
b) Structured delivery
c) Actual delivery
d) Symbolic delivery

Constructive delivery:
- Constructive delivery refers to a situation where the transfer of possession is done without physically handing over the goods.
- It is based on the concept of legal fiction, where certain acts or documents are considered equivalent to physical delivery.
- For example, handing over the key to a storage facility where the goods are stored can be considered constructive delivery.

Actual delivery:
- Actual delivery is the most common form of delivery.
- It involves the physical transfer of goods from one party to another.
- For example, when a seller hands over the goods to a buyer, it is considered actual delivery.

Symbolic delivery:
- Symbolic delivery refers to the transfer of possession through the use of symbols or representations.
- It is commonly used in cases where the physical transfer of goods is not practical or possible.
- For example, handing over the document of title, such as a bill of lading, can be considered symbolic delivery.

Structured delivery:
- Structured delivery is not a recognized form of delivery.
- It is not commonly used or defined in legal or business contexts.
- The term "structured" may be used in other contexts, such as structured settlement, but it does not pertain to the transfer of possession of goods.

In conclusion, among the options provided, structured delivery is not a form of delivery. The other options, constructive delivery, actual delivery, and symbolic delivery, are recognized forms of delivery in various legal and business contexts.