Answer:
B. Contract involving personal skill
Step-by-step explanation:
The operation in this example is risky and is related to a dangerous surgery which would be best performed by Edna. The contract that was made is relying on the experience that Edna has, and therefore cannot be passed on to someone with a lower skill level required for this operation.
In the case where Edna is unable to perform the surgery, the contract will have to be taken up by another surgeon with an equal or greater skill level required for the operation.