A service provider or Subject Matter Expert (SME) should not give a client free choice.
By this I mean that the client has contracted a provider or SME to provide the answer to a problem. Therefore, the provider or SME should use their expertise to guide the client to the answer that is best for the client. The provider or SME should not ask the client what they want to do but instead guide the client through what is standard, the best practice and the legal requirements to achieve the answer they need.
As the client is paying for the answer not to tell the provider or SME what should be done. As if the client already knows the answer and how to achieve it then they could have implemented the solution themselves and therefore have no reason to hire anyone else.
The provider or SME must look for how they can add value to the client by not only providing the answer to the question the client asked but to provide answers to questions that the client did not even know that they needed to ask.
Successful International Project Management 