Explanation:

- S: "Amortisation is an accounting technique" provides the definition that encompasses the whole concept being discussed.

- R: "used to periodically lower" explains the purpose or action of the technique.

- P: "the book-value of a loan or" introduces what is affected by this technique.

- Q: "an intangible asset over a set period of time" provides additional detail about what can have its value amortized.

- Option 1: S R P Q

- The order presented correctly follows the logical flow of explaining a concept.

- Option 2: R S P Q

- Starts with the purpose, which is less effective without the initial definition.

- Option 3: S R Q P

- Altering the order of P and Q disrupts the object and time period relationship.

- Option 4: R P S Q

- The order lacks an initial definition and doesn't logically sequence the purpose and objects.