Well, first off, Textbroker uses AP style, not APA style (Associated Press vs. American Psychological Association).
In general, AP style tends to be minimalist in punctuation and grammar. Commas are relatively rare, for example, and parentheses are strongly discouraged. Always look to cut and condense when writing in AP style.
There are several sites out there that are handy, and I would strongly recommend that you read the Textbroker Author Blog religiously. An investment into the online AP style guide is definitely worthwhile ($25).
Good luck on the test, it's certainly a beast. I've passed it, but I think I got a lucky draw and got a bunch of relatively easy question. My wife took it about a month after, and her questions were much more... ambiguous. Just keep studying and keep trying and you'll get it.