What Is the Downside of Vertical Integration

What is the downside of vertical integration?

A) Many products have a level of complexity and significance in the creation of value that are poorly served by vertical integration
B) There is technical complexity, exacting buyer standards and a variety of dependencies between buyer and seller
C) It swells fixed costs and may not well duplicate the motivation of owners of independent businesses
D) Many products and services, like complex components, engineering services or system installations, cannot be fully specified
E) It does not recognize the dynamics of decision making by the cross-functional work teams, which are becoming common at large firms