Question

Which of the following is an example of vertical integration?

purchasing competitors

purchasing suppliers

informally agreeing on prices

buying stock in competing companies

Answer 1

This should help you get the right answer.
http://www.investopedia.com/terms/v/verticalintegration.asp

Answer 2

Vertical integration is basically where a company reduces the 'steps' in producing a product/service, if that makes sense. For example, let's say that a company sells leather shoes.
Normally, they would have to contract with farmers that produce leather, other companies that produce rubber, and soforth, but with vertical integration, that same company would own all of those producers, so that the cost to produce shoes is less.
'B' is then, probably the most correct answer.