What is the correct way to model the input parameter for a façade operation that calls readyByAttribute?

Consider the entity and struct shown in the model:

What is the correct way to model the input parameter for a façade operation that calls readyByAttribute?
A . Type=SampleEntity1, Shadow Type=Key
B . Type=SampleStruct1, Shadow Type=unspecified
C . Type=SampleStruct1, Shadow Type=Key
D . Type=SampleEntity1, Shadow Type=unspecified

Answer: A