There are mud and water all over, making it hard for people to go through.
make sth hard 为复合宾语结构，sth为宾语，形容词hard为宾补。当宾语为不定式或that从句时，必须用虚指it作形式宾语，真正宾语（不定式或that从句）外置（即位于句末）。
非谓语动词作状语，其逻辑主语被默认为句子的主语。 Seen from the highest building, the cars and people are small. 句子主语与see是被动关系，所以用过去分词短语作状语，保持主动与被动的一致。
