I was correcting my homework and the correct answer was: "The students from Oxford are going to study nature in Kenya"
But I just learned that if the uncountables is followed by a preposition I should use "The" before.
Why is "The student from Oxford are going to study the nature in Kenya?" wrong?
"The students from Oxford are going to study nature in Kenya" Here the uncountable noun nature is used in a general sense, i.e the general nature of Kenya, not any specific nature like the nature of the social/urban/rural/wild etc. life of Kenya.
We use no article with nature, society, space and other abstract nouns when these have a general meaning.
I love nature. (NOT...the nature)
It isn't always easy to fit in with society. (NOT...the society)
We are just taking our first steps into space. (NOT...the space)
(From Michael Swan's PEU)
The rule you mention can only ever apply to a noun phrase that is modified by a prepositional phrase (and even then, I am sure there are exceptions).
In your sentence, the prepositional phrase is not modifying the preceding noun phrase; it's modifying the preceding verb phrase. It doesn't mean
The students from Oxford are going to study [nature in Kenya]."
It means
The students from Oxford are going to [[study nature] in Kenya]]."
Another way of phrasing this is, Kenya is where the students from Oxford are going to study nature.
Even in a situation where you did want to use "in Kenya" to modify a noun phrase describing what the students are studying, "the nature" would be a poor choice. "Nature" is not really used to refer to specific subsets of the natural word; only to the natural world as a whole. (As mahmud koya's answer mentions, "nature" is commonly used with a definite article when it has the alternate meaning of "the way something is naturally": "the nature of a seed is to grow" or "the nature of a fire is to burn".) The other answers list some alternative expressions you could use.
The uncountables/preposition rule doesn't apply for this example - student does not qualify as an uncountable, as the plural is students.
If your word was a true uncountable you would need to qualify it with the, such as women or men. Then you could write:
The men from Oxford are going to study nature in Kenya.
You also do not need to use the second the, before nature. Nature is not strictly an uncountable noun, and the sentence suggests the study of nature in general, rather than nature specific to Kenya. This would make sense but would probably be worded more specifically to fit better, such as
The men from Oxford are going to study the natural environment/wildlife in Kenya.
