Why Did Walmart Require Its Suppliers to Sign a Code

Why did Walmart require its suppliers to sign a code of basic labor and then hired outside auditing firms to inspect supplier factories?

A) Walmart wanted to maintain quality merchandise despite its discount reputation.
B) Walmart was working to build strategic partnerships within Asia.
C) Walmart was working towards collaborative merchandising.
D) Walmart was developing a "Made in America" campaign.
E) Walmart wanted to ensure supplier compliance of core labor standards.