第一句正确.
this主语makes 谓;it宾语;very hard宾补,for trees to grow真正宾语
这使得树很难生长.
宾语+宾补:改为句子就是
It is very hard for trees to grow.
this makes the tree very hard to grow.(加the指一类,正确,但意思不同了:这使得种树很难)
=this makes trees very hard to grow.(也正确,但意思不同了:见上句)
如果宾语+宾补:
改为句子:
Trees are very hard to grow.
=It is very hard to grow trees.
=To grow trees is very hard.
to grow的逻辑主语不是trees了.
而
this makes it very hard for trees to grow.to grow的逻辑主语是trees.