This question checks which country the 2019 World Happiness Report ranked first. The report ranks around 150 countries using factors like income, social support, life expectancy, freedom, trust, and generosity.
Finland's combination of trust, equality, and welfare support kept it in first place, so the correct answer is Finland.
This question tests recall of a single specific fact: which country was ranked number one in the 2019 World Happiness Report. A good way to work through it is to recall what is distinctive about each Nordic nation's standing in that particular year rather than treating all four as interchangeable.
Recognising that Finland was in the middle of its own streak at the top in 2019, unlike its neighbours who had each led in other years but not this one, points clearly to the answer.
Therefore, the correct answer is Finland.