Fill in the blank (_) in the following sentence from the following choices.
Sentence: Since Matthew studied physics while Ian studied English, _ knew a lot about science and testing.

Choice 1: Since Matthew studied physics while Ian studied English, Matthew knew a lot about science and testing.
Choice 2: Since Matthew studied physics while Ian studied English, Ian knew a lot about science and testing.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
1.