The best answer is C. You would hold a series of interviews at each of the manufacturing plants using the business scenarios technique. This will allow you to understand the systems and integrations with local partners. You would use stakeholder analysis to identify key players in the engagement, and to understand their concerns. You will then identify and document the key high-level stakeholder requirements for the architecture. You will then generate high level definitions of the baseline and target architectures.

This answer is based on the TOGAF standard, which recommends the following steps to initiate the architecture project1:

Establish the architecture project

Identify stakeholders, concerns, and business requirements

Confirm and elaborate business goals, business drivers, and constraints

Evaluate business capabilities

Assess readiness for business transformation

Define scope

Confirm and elaborate Architecture Principles, including business principles

Develop Architecture Vision

Define the Target Architecture value propositions and KPIs

Identify the business transformation risks and mitigation activities

Secure stakeholder and sponsor approval

The answer C covers most of these steps, by using the business scenarios technique to elicit and validate the business requirements, goals, drivers, and constraints, as well as the current and future states of the architecture2. The answer C also uses stakeholder analysis to identify and engage the key stakeholders, and to address their concerns and expectations3. The answer C also generates high level definitions of the baseline and target architectures, which can be used to develop the Architecture Vision and the value propositions4.

The other answers are not the best approach for architecture development, because:

Answer A focuses on researching vendor literature and conducting briefings with vendors, which is not the best way to understand the business needs and the current situation of the enterprise. Answer A also defines a preliminary Architecture Vision without involving the stakeholders or validating the requirements, which may lead to misalignment and lack of consensus.

Answer B conducts a pilot project that will enable vendors to demonstrate potential solutions, which is premature and costly at this stage of the architecture project. Answer B also does not address the stakeholder concerns or the current systems and integrations, which may result in gaps and risks. Answer B also develops the requirements after the pilot project, which may not reflect the actual business needs and goals.

Answer D develops baseline and target architectures for each of the manufacturing plants, which may not consider the enterprise-wide perspective and the potential benefits of a common ERP system. Answer D also does not involve the stakeholders or address their concerns, which may result in resistance and conflict. Answer D also does not define the business case or the performance metrics, which are essential for demonstrating the value and feasibility of the architecture.

1: The TOGAF Standard, Version 9.2 - Architecture Vision 2: The TOGAF Standard, Version 9.2 - Business Scenarios 3: [The TOGAF Standard, Version 9.2 - Stakeholder Management] 4: [The TOGAF Standard, Version 9.2 - Architecture Definition Document]