A, B - Incorrect: These options use the wrong auxiliary has (singular) for the subject limits (plural).

C - Incorrect: The pronoun they is ambiguous. Limits... have made difficulties for international chains... as they are competing... is awkward.

E - Incorrect: The pronouns it and they in this option are ambiguous.

D - Correct: This option uses the correct auxiliary have (plural) for the subject limits (plural). The idiom such as is used correctly to introduce an example, and the use of infinitive to compete is correct after the noun Walmart.