英格兰曾是一个森林茂密的国家。

England was once a ___densely wooded country.

墨西哥城是世界上人口最密集的城市之一。

Mexico City is one of the most ___densely populated cities in the world.

城市地区通常人口密集，导致各种社会问题。

Urban areas are often ___densely populated, leading to various social issues.