Rest & Sleep Inc

Rest & Sleep Inc. is a mattress manufacturing firm. By manufacturing related products such as bed covers, comforters and quilts, and pillows, it has gained significant competitive advantage as it has managed to create profits in all these markets as well. Rest & Sleep creates a challenge for the other companies in the market by providing unique value through its customer services and warranties. Which of the following terms best describes what Rest & Sleep Inc. is practicing?

A) Market penetration
B) Business unit strategy
C) Corporate strategy
D) Unrelated diversification