S1. The manhunt for the perpetrator of the crime spread across the entire state. S2. There was deep public anger triggered by the enormity of the crime. The second statement:

Statement S1 describes the consequence—an extensive statewide manhunt. Statement S2 describes the cause—deep public anger over the enormity of the crime. Logically, the public anger and the enormity of the crime existed before and led to the widespread manhunt. Therefore, S2 represents the precursor (cause) that led to the situation described in S1 (effect). The crime and the resultant anger came first; the manhunt followed. Hence, S2 'is a precursor to the first', making option (a) correct.