[译] 他们在校园里种了许多树。
[误] They plant a lot of trees in the campus.

[正] They plant a lot of trees on (the) campus.
[注] 表示“在校园里”，应该说 on (the) campus，其中定冠词可以省略，但不能以 in the school (在学校里) 类推，说成 in the campus。