SELECT 문에 왜 name이 안들어갈까요?

query the names of all the continents (COUNTRY.Continent) and their respective average city populations (CITY.Population) rounded down to the nearest integer.

여기서 names of all the continents라고해서

SELECT country.name

     , FLOOR(AVG(city.population))

FROM city

    INNER JOIN country ON CITY.CountryCode = COUNTRY.Code

GROUP BY country.continent

이렇게 했었는데요.. GROUP BY의 이름과 같아야하기 때문에 바뀐건가요..?ㅠㅠ

SELECT 문에 왜 name이 안들어갈까요?