The actual tense used here in the portuguese sentence is likely preterite perfect: "has happened". It is confusing in portuguese because that tense is called "perfeito", and what is called the "pretérito perfeito" is in fact the "preterite" ie "simple past". See the verbix chart for this verb, for an example.
Another conjugation that fits is the TER + VERB form of the imperfect indicative: "used to happen" / "was happening".
Because I could find a reference to both mood/aspect meanings in various sources, I expect all three translations should be accepted:
• What was happening in the country?
• What used to happen in the country?
• What has happened in the country?
On the other hand the listed answer "has been happening" is present perfect ("has been") and progressive (w/ continuous ending "-ing"). I don't see, not can I find a reference searching the past 40 minutes, how any TER + VERB in portguese becomes present perfect progressive. I think the answer is wrong and even if it is dialectal, it is a localization and very likely not representative of anything as large as all of Brazil.
The answer is perfectly ok, and all (save possible exceptions, of course) "pretérito perfeito composto" (Ter + past participle) in Portuguese indeed have a "repetition" meaning, thus matching English's present perfect continuous, and, when a period is present, the present perfect as well.
Portuguese does differ from other languages having "have + participle" structures.