Constructions like the one in the underlined section in this question can be difficult to make sense of. First try to understand the meaning of the sentence. To contrast with "early struggles for urban retailers are...," we should have something like "early struggles for suburban retailers are." However, it is preferable to move the verb so that it doesn't end the sentence (as it does in (C) and (D)), leaving us with: "are early struggles for suburban retailers." There's no need to repeat "early struggles," so we can replace those two words with the pronoun "those." Finally: "are those for suburban retailers," choice (A).

Choice (B) eliminates the parallelism between each type of retailer's early struggles by replacing "early struggles" with "experience." (C) and (D) end in a verb which, as noted, isn't what the GMAT prefers. (E) has no verb at all, so again, the parts of the sentences referring to the two types of retailers are not parallel.