It is the responsibility of the business analyst to ensure that the stakeholder with approval authority is comfortable and in agreement with the requirements and the business value they will generate. The business analyst can gain consensus by facilitating effective communication with accountable individuals and ensuring that all decision-makers are in agreement and accepting the requirements of the solution being delivered. 

Ideally, all stakeholders will be in agreement about the requirements, but where this is not the case and it is decided to proceed with some stakeholders, not in full agreement, it is important to assess the risks this poses to the initiative's successful delivery.

If we refer to our previous example, it will be the responsibility of the business analyst to ensure that both stakeholders agree on which family vehicle with which features would be most suitable for their needs.