The forest was so dense that sunlight barely reached the ground.

森林如此茂密，陽光幾乎無法到達地面。

The fog was so dense that visibility was almost zero.

霧氣如此濃密，能見度幾乎為零。

He's a bit dense when it comes to understanding complex instructions.

他在理解複雜指令方面有點遲鈍。

Only a truly dense person would fall for that trick.

只有真正愚蠢的人才會上那個當。