Fill in the blank (_) in the following sentence from the following choices.
Sentence: Elena passed the exam while Laura failed because _ studied hard for the exam leading up to it.

Choice 1: Elena passed the exam while Laura failed because Elena studied hard for the exam leading up to it.
Choice 2: Elena passed the exam while Laura failed because Laura studied hard for the exam leading up to it.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
1.