Choose any topic as long as it has two clear sides and is not agreed upon by most of society. I do not have a preference on what topic so whatever the writer chooses to write about will be fine as long as it satisfies the requirements in the guideline.
All applicants go through a series of tests that check their level of English and knowledge of formatting styles. The applicant is also required to present a sample of writing to the Evaluation Department. If you wish to find out more about the procedure, check out the whole process.