Simple past or past perfect in a subordinate phrase? [closed]

Should I use the simple past or the past perfect when describing an antecedent to a past event? For example:

• Laura passed her exam because she studied very hard
• Laura passed her exam because she had studied very hard

Solution 1:

I think either would be just as correct. However, as to which sounds more natural: To me at least, the latter form using past perfect (had studied) is clearer, because you're emphasizing that the studying occurred before the exam was passed.

From Wikipedia:

[Past perfect] is used to refer to an occurrence that at a past time had already been started.

So to emphasize that the studying had been done before the exam (which also occurred in the past), you can use past perfect.

Solution 2:

In "Laura passed her exam because she studied very hard", "she studied" is past tense, so it means that at some point in the past, she studied.

In "Laura passed her exam because she had studied very hard", "she had studied" is past perfect tense, so it means that at some point in that past, she studied, but that she definitely had finished studying before the statement was made.