Answer:
Intangibility
Step-by-step explanation:
When a service is purchased it is difficult to judge the quality or characteristics of a service. When a product is purchased it is easier to judge the quality or characteristics of a service.
The product can be compared with similar products that other companies are making, the price of different product varies along with the tangible aspects of the product for example the look and feel of a product.
Here, Sarah is concerned about whether or not the massage which will be given will cure her backache. This cannot be judged until after the massage is taken. This is the intangible aspect of services Sarah is concerned about.